Unit 3 — End of Topic Tests (reviewer copy: all keys and model answers visible)

End of Topic Test: How the table is organized (u03-t1 · 5 forms × 21 items · 105 total)

David's notes for James:
full notes file
# u03-t1 — notes/queries from David's side (U3-G1)

1. RATIONED REAL REVERSAL PAIRS (the gate's structural adjudication): only three REAL mass-reversal pairs exist (Te/I, Ar/K, Co/Ni) and all are rationed inside the scope lessons (PTB-005 article/WE/fluency; PTB-007 reuses them). Inventing a fake reversal pair from real elements was ruled out, so 3 recorded adjudicated_instance_families in gate_config.json cover the residue: A#14 (your demo-curated Co/Ni item with the true masses 58.93/58.69 - R8 task-change vs the PTB-005 fluency), A#15 (your pool seed's Te-before-I key + Ar/Cl distractor - PTB-005's own specNotes record the reuse), B#15 (Ar/K rotation of the cited-evidence case). B-E variants that needed reversal instances elsewhere use letter-element given-data surfaces (your pool-12 class). Enforced by the gate-local validate_with_adjudications.py wrapper over the untouched _shared validator (U2-G2 precedent); 2 A2-class task-idiom whitelist entries also recorded ('the periodic table outline is shown with four cells marked', 'the claim is wrong' - both recur across your own spec items in 2 lessons). Flag if any family should be redistributed.
2. NUMERIC UNITS (seq 1 period read, seq 2 group read - the two numeric ENTRY rows): your seeds carry an empty unit_label, so the exported answers complete it with count words ('period', 'group' - U2-G1 count-word precedent). Grading is on the numeric value only (exact integers, tolerance 0); decimal typings like '4.0' are accepted alternates; the sigFigs field is display metadata carried to satisfy the test numeric contract, not an assessed requirement (precisionAssessed:false, the U01-G2/G3 convention; per-item gradingNote states this).
3. SEED INSTANCE DEVIATIONS (all recorded in the item sources; full table in DAVID_REVIEW.md): pool[0] gallium period-read -> KRYPTON on form A (gallium = PTB-004/PTB-007 article instance AND PTB-007 student-seen fluency instance; your must_freshen flag executed); A#7 argon -> XENON (argon is a rationed Ar/K member + PTB-005/PTB-006 article instance; B#15 owns the load-bearing argon citation); A#8 zinc/cadmium -> niobium/tantalum; C#7 (seed rotation) target Group 15 -> Group 12, key cadmium (the digit 15 is spec text). Everything else about those seeds is structurally verbatim.
4. SEED DISTRACTOR/STEM DEVIATIONS per our authoritative QC model (correct-but-irrelevant-foil class): A#4 d1 (a TRUE electron-arrangement explanation) -> false same-substance-returns claim; A#15's three foils, A#16 d1, and A#19 d3 replaced with cleanly FALSE misconception-keyed claims; A#15/B#16/B#17/D#17 stems rescoped after blind review (two-defensible fixes). NOTA/AOTA scan over your pool = zero literal occurrences, so no NOTA replacements were needed on this gate; the substantive escape-hatch seats on pools 12/18 ('Neither...', 'cannot be decided...') were kept.
5. SAME-FORM KEY ECHO (both your seeds, both on form A): A#10 and A#16 keys are near-duplicates - each keys on the misfit pairs falling into behavior-matching columns with no hand swaps. Left verbatim as seeded (non-adjacent, seqs 10 and 16); flagged in case you want one re-keyed or one seed moved off form A.
6. FRQ HOME JUDGMENT CALL: the seeds file's capstones[] names PTB-007, but PTB-007 is narrative evidence-matching already anchored objectively by its three demo-curated mcqs (seqs 14/16/20), and PTB-004's prod_seeds list is EMPTY. The terminal FRQ was therefore AUTHORED on PTB-004 (the four-step gap method - heaviest-procedure-lesson doctrine, U2-G2/U2-G3 precedent): a Mendeleev-style gap-prediction scenario on letter elements X/Z/M, parts (a) method license / (b) neighbor-pattern predictions / (c) confirmation vs pattern-failure, rubric 30/40/30. The steady down-column trend is a stated scenario premise on every form (interpolation would otherwise be underdetermined - QC catch). Flag if you want the FRQ homed on PTB-007 instead.
7. CLEAN-ELEMENT SCARCITY (cross-form reuse disclosure): after excluding restricted materials (no period-7/radioactive instances under the binding instance rule), rationed reversal-pair members, and student-seen article/fluency instances, the usable clean-element registry is thin (P2: boron only; P4: V/Se/Kr; P5 x10; P6 x7). Some non-MATERIALS elements therefore repeat across forms (validator-silent by design; e.g. the Nb/Ta, Ru/Os, Rh/Ir, Sb/Bi pairs each serve two slots on different forms), and form C reuses zirconium and yttrium in two figures on different drawn axes (rows vs columns). Retake leakage between forms is the accepted cost - flag if any repeat should be redistributed.
8. TEN STANDING MINOR NOTES from our authoritative QC model (no fix applied): the weak-third-distractor plausibility class, mostly on your seed-designed shared-cell/two-names foils at seqs 3/4/8/12/16/19. Listed in the gate's solqc_report.md; advise if you want those seats strengthened.
9. Blind-review figure families 'periodic-table-rows' and 'periodic-table-columns' (period numbers 1-7 down the left / group numbers 1-18 across the top, marked cells with symbols) were rendered positionally by a gate-local packet augmenter; documented as a _shared make_blind_packet.py candidate for the maintainer, not applied this wave (_shared read-only). Every Unit-3 gate needs the same families.

Form A

PTB-001 · easy · recall · seq 1 · seed:U3-G1/pool[0] (PTB-001 gateItems[0], gallium period-read) - must_freshen_instance EXECUTED: gallium -> krypton (gallium = PTB-004/PTB-007 article instance AND PTB-007 student-seen fluency instance, U2-G1 zinc-66 precedent; recorded stage-1 flag); count-the-rows structure, answer value (4) and column-count diagnostic class verbatim; V-T6 contract completion: unit_label '' -> unit 'period' (count word, blueprint numeric-unit note), sigFigs null -> 1 countable display digit + integer:true + precisionAssessed:false (recorded stage-2 adjudication, flag for David/James) · numeric
The periodic table outline is shown with krypton's cell marked. Which period is krypton in?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCell: {"symbol": "Kr", "name": "krypton", "row": 4} · style: "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 4, in the table's last colum…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCell": {
   "symbol": "Kr",
   "name": "krypton",
   "row": 4
  },
  "style": "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 4, in the table's last column on the right edge"
 }
}
Answer: 4 period KEY
also accepted: period 4, Period 4, 4.0
wrongValueDiagnostics
[
 {
  "value": 18,
  "misconception": "you counted columns across — krypton's column is the eighteenth, but the period is the row",
  "feedback": "This answer is wrong — 18 comes from counting columns across. Krypton's cell sits in the last column, but the period is the row. Counting rows from the top, krypton's cell sits in row 4, so krypton is in Period 4."
 }
]
feedback
{
 "keyExplanation": "Find the row that holds the marked cell. Counting from the top, krypton's cell sits in row 4. Krypton is in Period 4.",
 "anticipatedWrong": [
  {
   "value": 18,
   "misconception": "you counted columns across — krypton's column is the eighteenth, but the period is the row",
   "feedback": "This answer is wrong — 18 comes from counting columns across. Krypton's cell sits in the last column, but the period is the row. Counting rows from the top, krypton's cell sits in row 4, so krypton is in Period 4."
  }
 ]
}
PTB-002 · easy · recall · seq 2 · seed:U3-G1/pool[3] (PTB-002 gateItems[0], tin figure-read) - stem/figure/answer/diagnostics VERBATIM; V-T6 contract completion only: unit_label '' -> unit 'group' (count word, blueprint numeric-unit note), sigFigs null -> 2 countable display digits + integer:true + precisionAssessed:false (recorded stage-2 adjudication, flag for David/James) · numeric
The periodic table outline is shown with tin's cell marked. Which group is tin in?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Sn", "name": "tin"} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Sn",
   "name": "tin"
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Answer: 14 group KEY
also accepted: group 14, Group 14, 14.0
wrongValueDiagnostics
[
 {
  "value": 4,
  "misconception": "you numbered only the tall columns — the middle block's ten columns count too, so tin's column is the fourteenth",
  "feedback": "This answer is wrong — 4 comes from numbering only the tall columns. Count every column, including the ten columns of the table's middle block: counting from the left, tin's cell sits in column 14, so tin is in Group 14."
 },
 {
  "value": 5,
  "misconception": "you read the row number — tin sits in row 5, but the group is the column",
  "feedback": "This answer is wrong — 5 is the row number. Tin sits in row 5, but the group is the column its cell sits in. Counting every column from the left, including the middle block, tin's cell sits in column 14, so tin is in Group 14."
 }
]
feedback
{
 "keyExplanation": "Find the column that holds the marked cell. Counting from the left and including the middle block, tin's cell sits in column 14. Tin is in Group 14.",
 "anticipatedWrong": [
  {
   "value": 4,
   "misconception": "you numbered only the tall columns — the middle block's ten columns count too, so tin's column is the fourteenth",
   "feedback": "This answer is wrong — 4 comes from numbering only the tall columns. Count every column, including the ten columns of the table's middle block: counting from the left, tin's cell sits in column 14, so tin is in Group 14."
  },
  {
   "value": 5,
   "misconception": "you read the row number — tin sits in row 5, but the group is the column",
   "feedback": "This answer is wrong — 5 is the row number. Tin sits in row 5, but the group is the column its cell sits in. Counting every column from the left, including the middle block, tin's cell sits in column 14, so tin is in Group 14."
  }
 ]
}
PTB-003 · easy · recall · seq 3 · seed:U3-G1/pool[6] (= PTB-003 gateItems[0]) - stem/options/misconception clauses/explanation VERBATIM (placement flags empty; no NOTA; no material instances; formatting-only: <p> strip + house feedback composition) · mcq4
Mendeleev's table combined two rules. Which pair states them?
List the elements by increasing atomic mass, and start new rows so that similar elements share columns. KEY
List the elements by increasing atomic number, and start new rows so that similar elements share columns.
List the elements by increasing atomic mass, and start new rows after every seventh element.
Group the elements by color and state, and order each group alphabetically.
PTB-006 · easy · recall · seq 4 · seed:U3-G1/pool[17] (= PTB-006 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA, zero placement flags; the electron-arrangement distractor is the spec's licensed gate-3 why-slot (extraNotes) and stays confined to this form | sol-loop-2 (SEED stem deviation, recorded): the electron-arrangement foil is TRUE later-course content, so the law-vs-explanation criterion is now explicit in the stem; option texts verbatim. | sol-loop-3 (SEED d1 replacement, recorded): the seed's electron-arrangement foil is TRUE later-course content and sol holds the clean-distractor line even with the criterion stated; replaced with a cleanly false same-substance-returns misconception (the A#19 merger class); stem reverted to the seed's own wording. · mcq4
Which statement is the periodic law itself?
Listed in order of increasing atomic number, elements with similar properties appear at regular intervals. KEY
Similar properties return because the same element appears again farther down the list, under a new name.
Elements in the same row of the periodic table have similar properties.
Every element's properties are fixed by its atomic mass.
PTB-001 · medium · application · seq 5 · seed:U3-G1/pool[2] (PTB-001 gateItems[2], James) - stem/options/feedback/explanations VERBATIM; additive figureSpec blind-containment only (markedCells 'row' fields + positional style, drawn content unchanged) · mcq4
The periodic table outline is shown with four cells marked: silver, iron, cesium, and aluminum. Which marked element sits in Period 5?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Ag", "name": "silver", "row": 5}, {"symbol": "Fe", "name": "iron", "row": 4}, {"symbol": "Cs", "name": "cesium", "row": 6}, {"symbol": "Al", "na… · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 3 (aluminum), 4 (iron)…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Ag",
    "name": "silver",
    "row": 5
   },
   {
    "symbol": "Fe",
    "name": "iron",
    "row": 4
   },
   {
    "symbol": "Cs",
    "name": "cesium",
    "row": 6
   },
   {
    "symbol": "Al",
    "name": "aluminum",
    "row": 3
   }
  ],
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 3 (aluminum), 4 (iron), 5 (silver), and 6 (cesium)"
 }
}
Silver. KEY
Iron.
Cesium.
Aluminum.
PTB-004 · medium · application · seq 6 · seed:pool[9] (verbatim - no freshness flags; PTB-004 gateItems[0], the license case) · mcq4
A chemist using Mendeleev's method finds an empty cell between known elements in one column. What can she write down for the missing element?
Predicted properties, read from the elements around the gap. KEY
Nothing, until a sample of the element is found and measured.
Exact measured values, taken from the two elements beside the gap.
A note that the column must be wrong.
PTB-002 · medium · application · seq 7 · seed:U3-G1/pool[5] (PTB-002 gateItems[2], James) - stem/options/feedback/explanations verbatim EXCEPT one forced instance freshening (SEED RULING, recorded): the non-key marked cell argon -> xenon (same drawn column 18, Group 18). Argon is a rationed Ar/K reversal-pair member and PTB-005/006 article instance; keeping it here collided cross-form with the seq-15 form-B item, where argon is the load-bearing historical fact. Additive blind-containment figureSpec enrichment as before; drawn content otherwise unchanged. · mcq4
The periodic table outline is shown with four cells marked: oxygen, phosphorus, fluorine, and xenon. Which marked element sits in Group 16?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "O", "name": "oxygen", "column": 16}, {"symbol": "P", "name": "phosphorus", "column": 15}, {"symbol": "F", "name": "fluorine", "column": 17}, {"s… · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — phosphorus's cell in column 15, oxygen's in column 16, fluori…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCells": [
   {
    "symbol": "O",
    "name": "oxygen",
    "column": 16
   },
   {
    "symbol": "P",
    "name": "phosphorus",
    "column": 15
   },
   {
    "symbol": "F",
    "name": "fluorine",
    "column": 17
   },
   {
    "symbol": "Xe",
    "name": "xenon",
    "column": 18
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — phosphorus's cell in column 15, oxygen's in column 16, fluorine's in column 17, xenon's in column 18"
 }
}
Oxygen. KEY
Phosphorus.
Fluorine.
Xenon.
PTB-003 · medium · application · seq 8 · seed:pool[7] (= PTB-003 gateItems[1], James) — must_freshen_instance executed: calcium/strontium -> niobium/tantalum (LOOP-1 re-freshening: the first pick zinc/cadmium put the MATERIALS word zinc on form A while the seq-7 form-B key owns zinc, and shared both instances with the adjacent seq-9 item); structure otherwise verbatim. Niobium (1801) and tantalum (1802) were in Mendeleev's working set and are the classic behave-alike group-5 pair chemists long confused. · mcq4
Niobium and tantalum behave alike. What does Mendeleev's method tell you about their places in his table?
They sit in the same column. KEY
They sit next to each other in the same row.
They sit at opposite ends of the table.
They share one cell, because the table has room for only one of them.
PTB-001 · medium · application · seq 9 · authored | LOOP-1 REWRITE: old set zinc/antimony/gold/cadmium put the MATERIALS words zinc (owner: seq-7 form-B key) and gold (owner: seq-7 form-E key) on form A and shared zinc/cadmium with the adjacent seq-8 pair; new set antimony/boron/cadmium/thallium keeps the key pair Cd+Sb (row 5) with a shared-column trap (B and Tl both in column 13) and a corner-touch trap (Cd/Tl) · mcq4
The periodic table outline is shown with four cells marked: antimony, boron, cadmium, and thallium. Which pair of marked elements is in the same period?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Sb", "name": "antimony", "row": 5, "column": 15}, {"symbol": "B", "name": "boron", "row": 2, "column": 13}, {"symbol": "Cd", "name": "cadmium", … · columnPositionNote: "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled" · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Sb",
    "name": "antimony",
    "row": 5,
    "column": 15
   },
   {
    "symbol": "B",
    "name": "boron",
    "row": 2,
    "column": 13
   },
   {
    "symbol": "Cd",
    "name": "cadmium",
    "row": 5,
    "column": 12
   },
   {
    "symbol": "Tl",
    "name": "thallium",
    "row": 6,
    "column": 13
   }
  ],
  "columnPositionNote": "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled",
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
 }
}
Cadmium and antimony KEY
Boron and thallium
Antimony and thallium
Cadmium and thallium
PTB-005 · medium · application · seq 10 · seed:U3-G1/pool[13] (= PTB-005 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA, zero placement flags · mcq4
Moseley's atomic-number order replaced a mass order that had worked for most elements. Why did chemists accept the change?
Every element landed in a column matching its behavior, no pairs left to swap by hand. KEY
Atomic numbers were easier to measure than atomic masses.
The new order rearranged most of the table, proving the old one wrong.
Moseley's reputation settled the matter.
PTB-002 · medium · application · seq 11 · authored (element-choice middle-block case, target Group 6: key chromium col 6 row 4; skip-block trap selenium col 16 - the sixth TALL column; row-read trap lead row 6; one-off trap vanadium col 5; instances registry-clean per the ledger) | LOOP-1 PATCH: key chromium -> molybdenum (same column 6, row 5): chromium is a MATERIALS word owned by the seq-7 form-D key; every trap value (5/16/14 vs target 6) is unchanged. | loop-1b: stem list reordered (molybdenum not first) - the 'four cells marked molybdenum' boundary gram recurred at three seqs. · mcq4
The periodic table outline is shown with four cells marked: lead, molybdenum, selenium, and vanadium. Which marked element sits in Group 6?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "Mo", "name": "molybdenum", "column": 6, "row": 5}, {"symbol": "V", "name": "vanadium", "column": 5, "row": 4}, {"symbol": "Se", "name": "seleniu… · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCells": [
   {
    "symbol": "Mo",
    "name": "molybdenum",
    "column": 6,
    "row": 5
   },
   {
    "symbol": "V",
    "name": "vanadium",
    "column": 5,
    "row": 4
   },
   {
    "symbol": "Se",
    "name": "selenium",
    "column": 16,
    "row": 4
   },
   {
    "symbol": "Pb",
    "name": "lead",
    "column": 14,
    "row": 6
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown"
 }
}
Molybdenum. KEY
Selenium.
Lead.
Vanadium.
PTB-006 · medium · application · seq 12 · authored (blueprint seq-12 contract; LOOP-1 RE-INSTANCE: titanium is a MATERIALS word owned by the seq-8 form-B pair and 18/22/40 are spec-dirty or shared numbers; instance = rhodium/iridium, consecutive group-9 members 32 places apart - this item is the bank's sole owner of the digits 45/77/32; distractor classes unchanged) | sol-loop-2: d2 fb '18 places' leftover fixed (spacing here is 32); 'full-strength' overstatement removed. · mcq4
Rhodium (atomic number 45) and iridium (atomic number 77) stand 32 places apart when the elements are lined up by atomic number, yet both are hard, silvery metals that resist corrosion and form compounds with matching recipes. According to the periodic law, what does this observation show?
One of the law's regular returns: similar behavior comes back at set spacings along the list, stacking the two into one column of the table. KEY
The law expects elements that behave the same way to sit side by side in the list, so one of these two must be misplaced.
The law covers only the early stretch of the list, where the repeat comes every 8, so it says nothing about a pair this far along.
An element's kind of behavior fades gradually in the elements after it, so the likeness must be much weaker than reported.
PTB-003 · medium · application · seq 13 · authored (no seed exists for the seq-13 case shape; blueprint rows[12]; element-free, digit-free) | sol-loop-2: categorical 'never changes/never reshuffled' scoped to the method's two rules (PTB-005/007 later teach the recorded hand swaps). · mcq4
A chemist building a table with Mendeleev's two rules is partway through a row, with the cards laid in order of increasing atomic mass. The next card's element behaves just like the element at the start of the current row. What does the method direct?
Start a new row with that card, so it lands in the column of the element it behaves like. KEY
Lay the card next in the current row, since the mass order says it comes next.
Pull the card out of the mass order and slot it beside the elements it resembles.
Keep laying cards until this row grows as long as the row above it, then start the next row.
PTB-007 · medium · application · seq 14 · seed:U3-G1/pool[18] (= PTB-007 gateItems[0] = demo_curated[0], James demo-gate) — stem/key/option texts/misconception clauses/explanation VERBATIM; placement flag freshness_scope_article NOT freshened by design (structural reversal-pair registry pressure; R8 task-change adjudication candidate recorded); no NOTA; formatting-only: <p> strip + house feedback composition · mcq4
Cobalt's atomic mass (58.93) is larger than nickel's (58.69), yet cobalt comes first in the modern table. Which version of the table handles this pair without a hand swap, and why?
The atomic-number table — cobalt's atomic number is smaller, so the order needs no patching. KEY
The mass-ordered table — close masses were allowed to trade places freely.
Both versions — the pair sits the same way under either ordering.
Neither version — the pair still has to be swapped by hand today.
PTB-005 · medium · application · seq 15 · seed:pool[14] (= PTB-005 gateItems[2], James) — VERBATIM: stem, key, all three distractors, misconception clauses and explanation byte-preserved (<p> strip + house feedback composition only); the Te/I + Ar/Cl option reuse is the spec's own recorded R8 task-change clause | sol-loop-2 (SEED stem deviation, recorded): the seed's foils are true-but-non-disproving facts by design; the stem now declares all options true, satisfying the clean-distractor standard without touching James's options. | sol-loop-3 (SEED distractor replacement, recorded): sol holds that true-but-non-disproving foils are barred even when declared; the three foils are now cleanly false claims (claim-as-fact / mass-revision-moves-cells / column-mass), each misconception-keyed; the key keeps James's Te-I fact verbatim and the R8 iodine adjudication still applies. Declaration stem reverted to the seed's question. · mcq4
A student claims the modern periodic table lists elements by increasing atomic mass. Which fact shows the claim is wrong?
Tellurium comes before iodine even though tellurium's atomic mass is larger. KEY
Every element in the table has a larger atomic mass than the element just before it, with no exceptions.
When an element's atomic mass is remeasured, its cell in the modern table moves to match.
Elements that stack in one column always have almost identical atomic masses.
PTB-007 · medium · application · seq 16 · seed:pool[19] = demo_curated[1] (verbatim - no freshness flags; PTB-007 gateItems[1], James demo-gate: the change<->evidence matching case for the reordering) | sol-loop-2 (DEMO-SEED stem deviation, recorded): the gap-confirmation foil is TRUE evidence for a DIFFERENT change; the stem declares every finding real, making mis-attribution the only wrongness. d2 fb no longer implies number equals mass for hydrogen. | sol-loop-3 (DEMO-SEED d1 replacement, recorded): the true gap-confirmation fact is now a cleanly FALSE history claim (crediting the reordering with the gap successes) that still exercises the same evidence-mix-up discrimination; the loop-2 declaration (factually inconsistent, per sol) is withdrawn and the demo stem restored. · mcq4
Match the change to its evidence: what convinced chemists that ordering by atomic number was right?
Every mass-misplaced pair fell into a column matching its behavior, no swaps needed. KEY
The gap predictions had failed under the mass-ordered table, and only the switch to atomic-number order finally made them come true.
Atomic numbers turned out to equal atomic masses for most elements.
The atomic-number table was easier to print.
PTB-004 · hard · transfer · seq 17 · seed:pool[10] (verbatim - no freshness flags; PTB-004 gateItems[1], the falsification-outcome case) · mcq4
Which outcome would have counted against Mendeleev's table?
A gap element discovered with properties unlike the ones predicted for its gap. KEY
A gap staying empty for several more years.
A newly discovered element fitting neatly into an existing column.
Two elements in the same column reacting in similar ways.
PTB-005 · hard · transfer · seq 18 · seed:U3-G1/pool[12] (= PTB-005 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA, zero placement flags; options c/d = recorded escape-hatch blind-review watch (blueprint contract, U2-G3 precedent) · mcq4
Element Q has a larger atomic mass than element R, but a smaller atomic number. Which element comes first in the modern periodic table?
Q, because the table orders elements by atomic number. KEY
R, because the table puts the lighter element first.
Neither — the pair must be swapped by hand.
It cannot be decided without knowing both elements' properties.
PTB-006 · hard · transfer · seq 19 · seed:pool[16] (verbatim - zero placement flags; PTB-006 gateItems[1], James: the coincidence-claim judgment on oxygen 8 / sulfur 16) | sol-loop-2 (seed fb deviation, recorded): 'the same spacing... all along the list' contradicted PTB-006's growing intervals. | sol-loop-3 (SEED d3 replacement, recorded): sol judged the two-forms-of-one-element foil so implausible it cued the key on a transfer item; replaced with the taught mass-similarity class used by every sibling form at this seq. · mcq4
Oxygen is element 8 and sulfur is element 16, and the two behave alike. A classmate calls that a coincidence. What does the periodic law call it?
One instance of a repeating pattern that runs through the whole list. KEY
A coincidence — two elements out of more than a hundred are bound to match.
An error in the numbering of one of the two elements.
A result of oxygen and sulfur having nearly the same atomic mass.
PTB-007 · hard · transfer · seq 20 · seed:pool[20] = demo_curated[2] (verbatim - no freshness flags; PTB-007 gateItems[2], James demo-gate: the gaps-as-weakness claim judgment) · mcq4
A student claims Mendeleev's gaps were a weakness of his table. Judge the claim against the historical record.
The gaps became strengths — elements discovered later matched the properties predicted for them. KEY
The claim is right — the gaps stayed empty and were quietly dropped.
The claim is right — Moseley's reordering existed to remove the gaps.
The claim is wrong, because the gaps showed that mass ordering was mistaken.
PTB-004 · medium · application · seq 21 · authored (unseeded by design - gate-wide zero FRQ seeds; blueprint rows[20] gap-prediction FRQ; letter-element column fragment: soft metals X/Z, partner M, recipe one-to-two, melting falls / vigor rises down the column) | sol-loop-2: the steady column trend is now a STATED premise (two endpoint values alone underdetermine the in-between prediction; PTB-004 supplies no interpolation rule, so the scenario supplies the trend). · frq
A chemist filling in a Mendeleev-style table has left one cell empty: the next known element in the mass order did not match that column's properties. The column now reads, from top to bottom: Element X, directly above the empty cell — a soft metal; melts only at a very high temperature; reacts slowly with element M; its compound with element M holds one atom of X for every two atoms of M. (the empty cell) Element Z, directly below the empty cell — a soft metal; melts at a much lower temperature than X; reacts quickly with element M; its compound with element M holds one atom of Z for every two atoms of M. Down this column of the table, each of these properties changes steadily from one cell to the next.
A chemist filling in a Mendeleev-style table has left one cell empty: the next known element in the mass order did not match that column's properties. The column now reads, from top to bottom: Element X, directly above the empty cell — a soft metal; melts only at a very high temperature; reacts slowly with element M; its compound with element M holds one atom of X for every two atoms of M. (the empty cell) Element Z, directly below the empty cell — a soft metal; melts at a much lower temperature than X; reacts quickly with element M; its compound with element M holds one atom of Z for every two atoms of M. Down this column of the table, each of these properties changes steadily from one cell to the next. (a) The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now. (b) Predict each of the missing element's properties: the recipe of its compound with element M, its melting behavior, and how quickly it reacts with element M. Justify each prediction by pointing to the properties of element X and element Z. (c) Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Part a. The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now.
Model: The method allows her to write the missing element's predicted properties, read from the elements around the gap — here, from element X above and element Z below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured.
Part b. Predict each of the missing element's properties: the recipe of its compound with element M, its melting behavior, and how quickly it reacts with element M. Justify each prediction by pointing to the properties of element X and element Z.
Model: Compound recipe with M: one atom of the missing element for every two atoms of M — element X and element Z both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — easier to melt than X but harder to melt than Z. Melting drops from X down to Z, and the missing element sits between them, so its melting behavior must continue that step-by-step drop. Reaction vigor with M: in between as well — quicker than X but slower than Z, continuing the same change down the column. None of these values are copied from either neighbor: X and Z set the pattern, and the prediction continues it.
Part c. Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Model: To confirm: the discovered element's measured properties must match the written predictions — the one-atom-to-two-atoms recipe with M, melting between Z's and X's, and reaction vigor with M between the two. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with M, or melting and vigor falling outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.
Full model answer. (a) The method allows her to write the missing element's predicted properties, read from the elements around the gap — here, from element X above and element Z below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured. (b) Compound recipe with M: one atom of the missing element for every two atoms of M — element X and element Z both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — easier to melt than X but harder to melt than Z. Melting drops from X down to Z, and the missing element sits between them, so its melting behavior must continue that step-by-step drop. Reaction vigor with M: in between as well — quicker than X but slower than Z, continuing the same change down the column. None of these values are copied from either neighbor: X and Z set the pattern, and the prediction continues it. (c) To confirm: the discovered element's measured properties must match the written predictions — the one-atom-to-two-atoms recipe with M, melting between Z's and X's, and reaction vigor with M between the two. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with M, or melting and vigor falling outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.

Form B

PTB-001 · easy · recall · seq 1 · seed:U3-G1/pool[1] (PTB-001 gateItems[1], rubidium figure-read) - stem/figure/answer/diagnostic VERBATIM (no stage-1 flags); V-T6 contract completion only: unit_label '' -> unit 'period', sigFigs null -> 1 countable display digit + integer:true + precisionAssessed:false (same recorded adjudication as form A) · numeric
The periodic table outline is shown with rubidium's cell marked. Which period is rubidium in?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCell: {"symbol": "Rb", "name": "rubidium", "row": 5} · style: "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 5, in the table's first colu…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCell": {
   "symbol": "Rb",
   "name": "rubidium",
   "row": 5
  },
  "style": "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 5, in the table's first column on the left edge"
 }
}
Answer: 5 period KEY
also accepted: period 5, Period 5, 5.0
wrongValueDiagnostics
[
 {
  "value": 1,
  "misconception": "you read the column number — rubidium sits in the first column, but the period is the row",
  "feedback": "This answer is wrong — 1 is the column number. Rubidium sits in the first column, but the period is the row its cell sits in. Counting rows from the top, rubidium's cell sits in row 5, so rubidium is in Period 5."
 }
]
feedback
{
 "keyExplanation": "Find the row that holds the marked cell. Counting from the top, rubidium's cell sits in row 5. Rubidium is in Period 5.",
 "anticipatedWrong": [
  {
   "value": 1,
   "misconception": "you read the column number — rubidium sits in the first column, but the period is the row",
   "feedback": "This answer is wrong — 1 is the column number. Rubidium sits in the first column, but the period is the row its cell sits in. Counting rows from the top, rubidium's cell sits in row 5, so rubidium is in Period 5."
  }
 ]
}
PTB-002 · easy · recall · seq 2 · seed:U3-G1/pool[4] (PTB-002 gateItems[1], strontium figure-read) - stem/figure/answer/diagnostic VERBATIM; V-T6 contract completion only: unit_label '' -> unit 'group', sigFigs null -> 1 countable display digit + integer:true + precisionAssessed:false (same recorded adjudication as form A). Strontium is registry-clean ONLY because the seq-8 pair freshens away from Ca/Sr (seed_placement pool-7 dependency) · numeric
The periodic table outline is shown with strontium's cell marked. Which group is strontium in?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Sr", "name": "strontium"} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Sr",
   "name": "strontium"
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Answer: 2 group KEY
also accepted: group 2, Group 2, 2.0
wrongValueDiagnostics
[
 {
  "value": 5,
  "misconception": "you read the row number — strontium sits in row 5, but the group is the column",
  "feedback": "This answer is wrong — 5 is the row number. Strontium sits in row 5, but the group is the column its cell sits in. Strontium's cell sits in the second column from the left, so strontium is in Group 2."
 }
]
feedback
{
 "keyExplanation": "Find the column that holds the marked cell. Strontium's cell sits in the second column from the left. Strontium is in Group 2.",
 "anticipatedWrong": [
  {
   "value": 5,
   "misconception": "you read the row number — strontium sits in row 5, but the group is the column",
   "feedback": "This answer is wrong — 5 is the row number. Strontium sits in row 5, but the group is the column its cell sits in. Strontium's cell sits in the second column from the left, so strontium is in Group 2."
  }
 ]
}
PTB-003 · easy · recall · seq 3 · seed:U3-G1/pool[8] (= PTB-003 gateItems[2]) - stem/options/misconception clauses/explanation VERBATIM (placement flags empty; no NOTA; no material instances; formatting-only: <p> strip + house feedback composition) · mcq4
When Mendeleev sorted his element cards, what information did each card carry?
The element's atomic mass and its known properties. KEY
The element's atomic number and its proton count.
The element's date of discovery and its discoverer.
Only the element's name.
PTB-006 · easy · recall · seq 4 · seed:U3-G1/pool[15] (= PTB-006 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA, zero placement flags · mcq4
For the periodic law's pattern to show itself, how must the elements be listed?
In order of increasing atomic number. KEY
In order of increasing atomic mass.
In alphabetical order of their names.
Grouped by state at room temperature.
PTB-001 · medium · application · seq 5 · authored (James's PTB-001 four-cell period-read structure kept verbatim-parallel; fresh set tantalum/vanadium/niobium/rhenium - the vanadium-niobium-tantalum group-5 column plus rhenium gives a one-row-too-high AND a one-row-too-low trap around the key; loop-1 patch: bismuth -> rhenium and vanadium moved out of first list position, killing the 'four cells marked vanadium' and 'and bismuth which marked' cross-seq instance grams vs the row07 D/E stems) · mcq4
The periodic table outline is shown with four cells marked: tantalum, vanadium, niobium, and rhenium. Which marked element sits in Period 5?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Ta", "name": "tantalum", "row": 6}, {"symbol": "V", "name": "vanadium", "row": 4}, {"symbol": "Nb", "name": "niobium", "row": 5}, {"symbol": "Re… · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 4 (vanadium), 5 (niobi…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Ta",
    "name": "tantalum",
    "row": 6
   },
   {
    "symbol": "V",
    "name": "vanadium",
    "row": 4
   },
   {
    "symbol": "Nb",
    "name": "niobium",
    "row": 5
   },
   {
    "symbol": "Re",
    "name": "rhenium",
    "row": 6
   }
  ],
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 4 (vanadium), 5 (niobium), and 6 (tantalum and rhenium)"
 }
}
Niobium. KEY
Vanadium.
Tantalum.
Rhenium.
PTB-004 · medium · application · seq 6 · seed:pool[11] (verbatim - no freshness flags; PTB-004 gateItems[2], the step-ordering case designed by the spec to avoid re-asking the fluency reason questions) · mcq4
Put the steps of Mendeleev's gap method in order.
Notice that the next element does not match the column — leave the cell empty — predict the missing element's properties from its neighbors — compare later discoveries against the prediction. KEY
Leave the cell empty — notice that the next element does not match the column — compare later discoveries against the prediction — predict the missing element's properties from its neighbors.
Predict the missing element's properties from its neighbors — notice that the next element does not match the column — leave the cell empty — compare later discoveries against the prediction.
Notice that the next element does not match the column — force it into the column anyway — predict its properties from its neighbors — compare later discoveries against the prediction.
PTB-002 · medium · application · seq 7 · authored (seed-parallel marked-set rotation: palladium/copper/zinc/boron, key zinc Group 12) | LOOP-1 PATCH: copper -> iridium (column 9): copper is a MATERIALS word owned by the row02 form-D seed-parallel item; iridium keeps a near-block column read with the key zinc untouched. | sol-loop-2: style enumeration re-derived from the markedCells (loop-1 token swap left the OLD element's column on the swapped-in name - QB 3.9 leftover class, caught by sol). · mcq4
The periodic table outline is shown with four cells marked: iridium, palladium, zinc, and boron. Which marked element sits in Group 12?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "Ir", "name": "iridium", "column": 9}, {"symbol": "Pd", "name": "palladium", "column": 10}, {"symbol": "Zn", "name": "zinc", "column": 12}, {"sym… · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — iridium's cell in column 9, palladium's in column 10, zinc's …
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCells": [
   {
    "symbol": "Ir",
    "name": "iridium",
    "column": 9
   },
   {
    "symbol": "Pd",
    "name": "palladium",
    "column": 10
   },
   {
    "symbol": "Zn",
    "name": "zinc",
    "column": 12
   },
   {
    "symbol": "B",
    "name": "boron",
    "column": 13
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — iridium's cell in column 9, palladium's in column 10, zinc's in column 12, boron's in column 13"
 }
}
Zinc. KEY
Palladium.
Iridium.
Boron.
PTB-003 · medium · application · seq 8 · authored · mcq4
Titanium and zirconium react in similar ways. When the elements are laid out by Mendeleev's method, where do these two end up?
Stacked in the same column, each in its own row. KEY
Side by side in the same row.
At opposite ends of the table, separated by the mass gap.
In one shared cell, since the table has room for only one of them.
PTB-001 · medium · application · seq 9 · authored | LOOP-1 REWRITE: old set molybdenum/tungsten/boron/platinum put the MATERIALS words tungsten (owner: seq-7 form-E) and platinum (owner: seq-7 form-D) on form B and tripled boron on the form; new set molybdenum/selenium/hafnium/osmium keys Hf+Os (row 6) | loop-1b: stem list reordered (molybdenum last; osmium-first avoids the 'and osmium which marked' clash with the seq-5 form-D stem). · mcq4
The periodic table outline is shown with four cells marked: osmium, hafnium, selenium, and molybdenum. Which pair of marked elements is in the same period?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Mo", "name": "molybdenum", "row": 5, "column": 6}, {"symbol": "Se", "name": "selenium", "row": 4, "column": 16}, {"symbol": "Hf", "name": "hafni… · columnPositionNote: "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled" · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Mo",
    "name": "molybdenum",
    "row": 5,
    "column": 6
   },
   {
    "symbol": "Se",
    "name": "selenium",
    "row": 4,
    "column": 16
   },
   {
    "symbol": "Hf",
    "name": "hafnium",
    "row": 6,
    "column": 4
   },
   {
    "symbol": "Os",
    "name": "osmium",
    "row": 6,
    "column": 8
   }
  ],
  "columnPositionNote": "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled",
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
 }
}
Hafnium and osmium KEY
Molybdenum and hafnium
Selenium and molybdenum
Selenium and osmium
PTB-005 · medium · application · seq 10 · authored (claim-response rotation per the blueprint seq-10 contract: {novelty-of-method restating the classmate's claim, better-mass-precision, old-order-failed-for-most scale overstatement}; key invariant — the taught acceptance fact; no named pair, no digits) · mcq4
A classmate says chemists switched to Moseley's atomic-number order just because X-rays were the newest technology of the day. What actually persuaded chemists to adopt the new order?
In the new list, every element sat in a column matching its behavior, and no pair needed swapping by hand anymore. KEY
The classmate is right — the X-ray method was newer and more impressive than weighing, and that settled it.
Moseley's X-rays measured the atomic masses more precisely, and the corrected masses fixed the old list.
The old mass order had put most elements in the wrong columns, so almost any replacement would have been an improvement.
PTB-002 · medium · application · seq 11 · authored (statement-choice case, LOOP-1 REWRITE: the old boron instance was form B's THIRD boron and its stem gram collided with the row02 form-C stem; thallium/antimony/cadmium alternates each collided with a single-cell stem elsewhere or a same-form cell, and yttrium's right-edge count (16) collides with the form-A seq-7/19 number 16 - ruthenium col 8 row 5 keeps every statement value inside the numeric ignore range: 8 / no-number / 5 / 11) · mcq4
The periodic table outline is shown with ruthenium's cell marked. Which statement correctly gives ruthenium's group?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Ru", "name": "ruthenium", "column": 8, "row": 5} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Ru",
   "name": "ruthenium",
   "column": 8,
   "row": 5
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Ruthenium is in Group 8 — counting every column from the left edge, including the ten middle-block columns, its cell sits in the eighth column. KEY
Ruthenium has no group number — only the tall columns on the left and right sides of the table are numbered, and ruthenium's cell sits in the middle block.
Ruthenium is in Group 5 — an element's group is the row its cell sits in, and ruthenium's cell sits in the fifth row.
Ruthenium is in Group 11 — the groups are numbered starting from the right-hand edge, and ruthenium's cell is the eleventh column in from the right.
PTB-006 · medium · application · seq 12 · authored (LOOP-1 RE-INSTANCE: zinc is a MATERIALS word owned by the seq-7 form-B key and 18/30/48 were shared or spec-dirty; instance = antimony/bismuth, consecutive group-15 members - sole owner of the digits 51/83, interval left unstated; lab-handbook substitution surface kept; distractor classes: fixed-8-universal-count / steady-drift / column-as-cause) | sol-loop-2: interchangeability overstatement removed; 'metals' dropped (antimony is conventionally a metalloid). · mcq4
A reference handbook notes that antimony (atomic number 51) and bismuth (atomic number 83) form the same kinds of compounds with the same partners, following matching recipes. The two sit far apart in the numbered list of elements. How does the periodic law account for this?
Antimony's kind of behavior returns a regular interval later: the law's pattern brings look-alikes back all along the list, so the pair shares a column. KEY
The law's matches come exactly every 8 elements, so a pair separated this widely falls outside the pattern and needs a different explanation.
Properties change steadily from the first element to the last, so the law would treat two distant elements forming matching compounds as nothing more than a recording error.
The two react alike because the table assigned them one column; their places in the numbered list have nothing to do with it.
PTB-003 · medium · application · seq 13 · authored (element-free, digit-free) · mcq4
A student re-creating Mendeleev's layout has filled part of a row, keeping the cards in order of increasing atomic mass. The next card up behaves just like the element heading the row. Which move does the method call for?
Ending the row and starting a new one with that card, right below the element it matches. KEY
Placing the card in the next spot of the current row, so the single line runs on unbroken.
Moving the card back up the line so it sits next to the element it behaves like.
Finishing the row to a fixed length first, and only then starting a new one.
PTB-007 · medium · application · seq 14 · authored (seed case on a letter-element relational surface — pool-12 class; letters J/L claimed; relations only, no fabricated numeric data) · mcq4
Element J's atomic mass is larger than element L's, yet J comes first in the modern table. Which version of the table seats this pair without a hand swap, and why?
The atomic-number table — J's atomic number is smaller than L's, so the order needs no patching. KEY
The mass-ordered table — pairs that behave alike were allowed to trade places freely.
Both versions — either ordering leaves the pair sitting the same way, so a swap was never needed.
Neither version — even today the pair must still be swapped by hand.
PTB-005 · medium · application · seq 15 · authored (real-fact citation rotated to the Ar/K worked-example pair under a recorded R8 task-change candidate — WE rule-application -> cited counter-evidence, the spec's own Te/I pattern; agreeing-pair foil ruthenium/rhodium, fresh) | sol-loop-2: same all-true declaration as the form-A seed. | sol-loop-3: foils now cleanly false (claim-as-fact / heaviest-first inversion / mass-repair rule); the Ar-K key fact untouched (R8 adjudication stands); declaration stem reverted. | sol-loop-4: keyExplanation re-enumerated against the loop-3 options (stale ruthenium/discovery-date references removed); d2 feedback's invalid 'one cell cannot test the claim' clause dropped. | sol-loop-5: d1's wrongness no longer rides an absolute qualifier; discovery-order misconception instead (E#15 uses the same taught class at this seq on another form). · mcq4
A classmate claims the elements of the modern periodic table are arranged from smaller atomic mass to larger. Which fact shows this claim is wrong?
Argon comes before potassium even though argon's atomic mass is larger. KEY
The table hands out places by discovery date: the earlier an element was found, the earlier its cell.
The table's very first cell holds the heaviest element of all.
Whenever two neighboring elements' masses are found to be out of order, the modern table swaps their two cells to restore mass order.
PTB-007 · medium · application · seq 16 · authored (MIRROR change->evidence case: the pattern's own backing; wrong-evidence foil runs the seed's class-split in the opposite direction) | LOOP-2 PATCH (blind F2, r1): the reordering-evidence distractor was defensibly ALSO evidence that the column pattern was real; the stem now scopes the evidence window to decades before atomic numbers were measured (historically exact: gap confirmations 1875-1886 vs Moseley 1913), which excludes the reordering option while keeping it tempting. | sol-loop-2: all-real declaration added (the time-scoped foils are true later findings by design). | sol-loop-3: the two true-later-findings foils are now cleanly false history claims (no-swaps-ever mass order; anachronistic atomic-number confirmation, the D#3 anachronism class); declaration withdrawn, time scope kept in the question clause. | sol-loop-4: d3 convenience foil (possibly-true-irrelevant) replaced with a cleanly false all-gaps-needed acceptance claim; keyExplanation extended to name every foil's error. | sol-loop-5 REDESIGN: the F2-prone reordering-evidence foil is gone entirely; every foil is now false in substance against taught facts (varied row lengths PTB-003; atomic-number anachronism; first-confirmations acceptance), none hinges on a quantifier, and the time scope lives in the foils' own content rather than the stem. · mcq4
In the table's story, which evidence showed that Mendeleev's pattern of similar elements sharing columns was real?
Newly discovered elements matched the properties that had been predicted for the gaps. KEY
The mass-ordered rows all came out the same length, showing the pattern had been built in from the start.
Mendeleev measured each element's atomic number and showed that the columns lined up with it.
Acceptance arrived when the last of the table's gaps was finally filled, closing out the story.
PTB-004 · hard · transfer · seq 17 · authored (RIVAL-CHEMIST rotation per the blueprint seq-17 contract; foils = gap-match-confirms, patience-as-failure re-worded, accidental-discovery overreach; key invariant - the one falsifying outcome; elementless, no digits) | LOOP-2 PATCH (blind advisory, r1): "prove Mendeleev's table wrong / would have done it" overstated what one broken gap prediction shows; reframed to the seed's own evidence wording (counted against). | LOOP-3 PATCH (reblind F2, r3): the loop-2 softening to "counted against" made the empty-gap option defensible as weak evidence; the frame is now catching the table in a FALSE PREDICTION — a still-empty gap is no discovery and catches nothing, while one broken prediction is exactly a catch (no overstatement of whole-table falsification either). · mcq4
A rival chemist wanted to catch Mendeleev's table in a false prediction. Which discovery would have done it?
Finding a gap element whose measured properties disagreed with the prediction written for its gap. KEY
Finding an element for one of the gaps whose properties turned out to match the prediction written for it.
Showing that one of the gaps had stayed empty despite a long search.
Discovering a new element by accident, without using the table at all.
PTB-005 · hard · transfer · seq 18 · authored (mirrored-pick rotation per the blueprint seq-18 contract: fresh letters X/Z, nearly-equal masses license the tie foil, second-named element keys; distractors {mass-order re-worded (structural foil), tie-rule, wrong-particle} — PTB-005 fluency-recorded classes; no real elements, no digits) · mcq4
Element X's atomic mass is slightly smaller than element Z's, but X's atomic number is larger. Which element comes first in the modern periodic table?
Z, because atomic number alone sets the order, and Z's is the smaller. KEY
X, because the lighter element always comes first.
Either — atomic masses this close count as a tie, so both orders are allowed.
Neither can be placed until both elements' neutron counts are known.
PTB-006 · hard · transfer · seq 19 · authored (luck-claim rotation: krypton 36 / xenon 54, interval 18; foils = accept-luck / mass-similarity (fluency-2 class) / fixed-universal-count (fluency-3 class)) | LOOP-1 PATCH: option d rephrased numberless (the digit 18 is spec text of four scope lessons). · mcq4
Krypton is element 36 and xenon is element 54, and the two behave alike. A lab partner says the match is pure luck. What does the periodic law call it?
One instance of the repeating pattern that runs all along the list. KEY
Pure luck — among so many elements, some pair is bound to behave alike.
A result of krypton and xenon having nearly equal atomic masses.
Proof that one single count, repeated from the very first element to the last, spaces out every one of the look-alike pairs.
PTB-007 · hard · transfer · seq 20 · authored (REORDERING-SCOPE claim judgment: how much of the design did Moseley's reordering overturn; foils = rebuilt-from-scratch / denial-of-the-flaw wrong-reason / predictions-thrown-out crossed-chapters) · mcq4
A student claims that Moseley's reordering proved Mendeleev's table had been wrong from the start. Judge the claim against the historical record.
The claim is wrong — only the ordering quantity changed; the columns of similar elements and the confirmed predictions stood. KEY
The claim is right — the new ordering rebuilt the table from scratch, keeping nothing of the original design.
The claim is wrong, because mass order had never misplaced a single element, so there was nothing to prove wrong.
The claim is right — the confirmed gap predictions had to be thrown out once the ordering quantity changed.
PTB-004 · medium · application · seq 21 · authored (blueprint rows[20] gap-prediction FRQ; letter-element column fragment: sharp-smelling nonmetals G/J, partner T, recipe one-to-one, melting rises / vigor falls down the column) | sol-loop-2: the steady column trend is now a STATED premise (two endpoint values alone underdetermine the in-between prediction; PTB-004 supplies no interpolation rule, so the scenario supplies the trend). · frq
A chemist has left one cell of a column empty partway down the mass order: the next known element did not match the column's properties. The column fragment reads, top to bottom: Element G, directly above the empty cell — a sharp-smelling nonmetal; melts at a low temperature; reacts fiercely with element T; its compound with element T holds one atom of G for every one atom of T. (the empty cell) Element J, directly below the empty cell — a sharp-smelling nonmetal; melts at a much higher temperature than G; reacts only mildly with element T; its compound with element T holds one atom of J for every one atom of T. Down this column of the table, each of these properties changes steadily from one cell to the next.
A chemist has left one cell of a column empty partway down the mass order: the next known element did not match the column's properties. The column fragment reads, top to bottom: Element G, directly above the empty cell — a sharp-smelling nonmetal; melts at a low temperature; reacts fiercely with element T; its compound with element T holds one atom of G for every one atom of T. (the empty cell) Element J, directly below the empty cell — a sharp-smelling nonmetal; melts at a much higher temperature than G; reacts only mildly with element T; its compound with element T holds one atom of J for every one atom of T. Down this column of the table, each of these properties changes steadily from one cell to the next. (a) The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now. (b) Predict each of the missing element's properties: the recipe of its compound with element T, its melting behavior, and how vigorously it reacts with element T. Justify each prediction by pointing to the properties of element G and element J. (c) Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Part a. The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now.
Model: The method allows her to write the missing element's predicted properties, read from the elements around the gap — here, from element G above and element J below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured.
Part b. Predict each of the missing element's properties: the recipe of its compound with element T, its melting behavior, and how vigorously it reacts with element T. Justify each prediction by pointing to the properties of element G and element J.
Model: Compound recipe with T: one atom of the missing element for every one atom of T — element G and element J both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — it should melt at a higher temperature than G but a lower temperature than J, because melting climbs from G down to J and the missing element sits between them. Reaction vigor with T: in between as well — less fierce than G but livelier than J, continuing the same change down the column. None of these values are copied from either neighbor: G and J set the pattern, and the prediction continues it.
Part c. Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Model: To confirm: the discovered element's measured properties must match the written predictions — the one-atom-to-one-atom recipe with T, melting between G's and J's, and reaction vigor with T between the two. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with T, or melting and vigor falling outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.
Full model answer. (a) The method allows her to write the missing element's predicted properties, read from the elements around the gap — here, from element G above and element J below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured. (b) Compound recipe with T: one atom of the missing element for every one atom of T — element G and element J both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — it should melt at a higher temperature than G but a lower temperature than J, because melting climbs from G down to J and the missing element sits between them. Reaction vigor with T: in between as well — less fierce than G but livelier than J, continuing the same change down the column. None of these values are copied from either neighbor: G and J set the pattern, and the prediction continues it. (c) To confirm: the discovered element's measured properties must match the written predictions — the one-atom-to-one-atom recipe with T, melting between G's and J's, and reaction vigor with T between the two. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with T, or melting and vigor falling outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.

Form C

PTB-001 · easy · recall · seq 1 · authored (James's PTB-001 figure-read structure kept verbatim-parallel; fresh instance: vanadium - spec-clean, non-MATERIALS, middle-block cell so the column-count trap value (5) sits adjacent to the true answer (4), sharpening the row-vs-column discrimination) · numeric
The periodic table outline is shown with vanadium's cell marked. Which period is vanadium in?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCell: {"symbol": "V", "name": "vanadium", "row": 4} · style: "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 4, inside the table's middle…
raw spec
{
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  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCell": {
   "symbol": "V",
   "name": "vanadium",
   "row": 4
  },
  "style": "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 4, inside the table's middle block near its left side"
 }
}
Answer: 4 period KEY
also accepted: period 4, Period 4, 4.0
wrongValueDiagnostics
[
 {
  "value": 5,
  "misconception": "you counted columns across — vanadium's cell sits in the fifth column, but the period is the row",
  "feedback": "This answer is wrong — 5 comes from counting columns across. Vanadium's cell sits in the fifth column, but the period is the row. Counting rows from the top, vanadium's cell sits in row 4, so vanadium is in Period 4."
 }
]
feedback
{
 "keyExplanation": "Find the row that holds the marked cell. Counting from the top, vanadium's cell sits in row 4. Vanadium is in Period 4.",
 "anticipatedWrong": [
  {
   "value": 5,
   "misconception": "you counted columns across — vanadium's cell sits in the fifth column, but the period is the row",
   "feedback": "This answer is wrong — 5 comes from counting columns across. Vanadium's cell sits in the fifth column, but the period is the row. Counting rows from the top, vanadium's cell sits in row 4, so vanadium is in Period 4."
  }
 ]
}
PTB-002 · easy · recall · seq 2 · authored (James's PTB-002 figure-read structure kept verbatim-parallel; fresh instance: boron, classroom-set rule; right-side cell so both taught traps have defined values, mirroring the tin seed's diagnostic pair) · numeric
The periodic table outline is shown with boron's cell marked. Which group is boron in?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "B", "name": "boron"} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
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 "figureShape": "stimulus",
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  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "B",
   "name": "boron"
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Answer: 13 group KEY
also accepted: group 13, Group 13, 13.0
wrongValueDiagnostics
[
 {
  "value": 3,
  "misconception": "you numbered only the tall columns — the middle block's ten columns count too, so boron's column is the thirteenth",
  "feedback": "This answer is wrong — 3 comes from numbering only the tall columns. Count every column, including the ten columns of the table's middle block: counting from the left, boron's cell sits in column 13, so boron is in Group 13."
 },
 {
  "value": 2,
  "misconception": "you read the row number — boron sits in row 2, but the group is the column",
  "feedback": "This answer is wrong — 2 is the row number. Boron sits in row 2, but the group is the column its cell sits in. Counting every column from the left, including the middle block, boron's cell sits in column 13, so boron is in Group 13."
 }
]
feedback
{
 "keyExplanation": "Find the column that holds the marked cell. Counting from the left and including the middle block, boron's cell sits in column 13, the first column after the middle block. Boron is in Group 13.",
 "anticipatedWrong": [
  {
   "value": 3,
   "misconception": "you numbered only the tall columns — the middle block's ten columns count too, so boron's column is the thirteenth",
   "feedback": "This answer is wrong — 3 comes from numbering only the tall columns. Count every column, including the ten columns of the table's middle block: counting from the left, boron's cell sits in column 13, so boron is in Group 13."
  },
  {
   "value": 2,
   "misconception": "you read the row number — boron sits in row 2, but the group is the column",
   "feedback": "This answer is wrong — 2 is the row number. Boron sits in row 2, but the group is the column its cell sits in. Counting every column from the left, including the middle block, boron's cell sits in column 13, so boron is in Group 13."
  }
 ]
}
PTB-003 · easy · recall · seq 3 · authored (rules case rotated onto a summary-pick surface; element-free, digit-free) · mcq4
A museum display about early chemistry sums up how Mendeleev built his table. Which summary matches his method?
He arranged the elements from lightest to heaviest by atomic mass, and began a new row wherever the pattern of behavior started over. KEY
He arranged the elements from smallest to largest atomic number, and began a new row wherever the pattern of behavior started over.
He arranged the elements by atomic mass, and cut the line into rows of equal length so the chart stayed tidy.
He grouped the elements by their appearance, and then listed each group alphabetically by name.
PTB-006 · easy · recall · seq 4 · authored (statement-case rotation per the blueprint seq-4 contract: parallel what-happens-along-the-list set {steady-change-as-law, fixed-8-universal-count, neighbor-clustering} — all PTB-006 fluency-recorded misconception classes; key sentence invariant — the taught fact) | sol-loop-2: d2's wrongness no longer hinges on universal qualifiers; the fixed-single-spacing claim is false in substance under PTB-006's growing intervals. · mcq4
A student is asked to state the periodic law. Which sentence states the law correctly?
Listed in order of increasing atomic number, elements with similar properties appear at regular intervals. KEY
Listed in order of increasing atomic number, properties change steadily from the first element to the last, with no repeats.
Listed in order of increasing atomic number, similar elements return at one fixed spacing that stays the same from the beginning of the list to the end.
Listed in order of increasing atomic number, elements with similar properties always sit next to each other.
PTB-001 · medium · application · seq 5 · authored (James's PTB-001 four-cell period-read structure kept verbatim-parallel; fresh set rhodium/palladium/xenon/hafnium - form C's remaining clean-element stock is period-5/6 only, so the three distractors share row 5 while hafnium is the lone period-6 cell; key still the only cell in the target row) · mcq4
The periodic table outline is shown with four cells marked: rhodium, palladium, xenon, and hafnium. Which marked element sits in Period 6?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Rh", "name": "rhodium", "row": 5}, {"symbol": "Pd", "name": "palladium", "row": 5}, {"symbol": "Xe", "name": "xenon", "row": 5}, {"symbol": "Hf"… · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 5 (rhodium, palladium,…
raw spec
{
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 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Rh",
    "name": "rhodium",
    "row": 5
   },
   {
    "symbol": "Pd",
    "name": "palladium",
    "row": 5
   },
   {
    "symbol": "Xe",
    "name": "xenon",
    "row": 5
   },
   {
    "symbol": "Hf",
    "name": "hafnium",
    "row": 6
   }
  ],
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 5 (rhodium, palladium, and xenon) and 6 (hafnium)"
 }
}
Hafnium. KEY
Xenon.
Rhodium.
Palladium.
PTB-004 · medium · application · seq 6 · authored (WHAT-THE-GAP-MEANS case; foils = PTB-004 fluency-1 misconception families re-instanced: gap-as-error / layout-spacer / deleted-element) · mcq4
One column of Mendeleev's table contains an empty cell with predicted values written beside it. Under his method, what does that empty cell stand for?
An element that exists but has not yet been discovered. KEY
A measurement that went wrong and still needs redoing.
A spacer that keeps the table's rows the same length.
An element removed from the table for not fitting its column.
PTB-002 · medium · application · seq 7 · authored (James's PTB-002 figure-read structure kept verbatim-parallel; LOOP-1 REWRITE: the v1 target Group 15 put the digit 15 in the stem - 15 is spec text of PTB-001/PTB-002 - and the old key arsenic is a MATERIALS word owned by the seq-9 form-D item and adjacent to the old seq-8 arsenic pair; new set cadmium KEY G12 / thallium 13 / molybdenum 6 / krypton 18, all spec-clean non-MATERIALS, target digit 12 inside the numeric ignore range) | loop-1b: stem list reordered (cadmium first) - kills the shared molybdenum-first boundary gram. · mcq4
The periodic table outline is shown with four cells marked: cadmium, molybdenum, thallium, and krypton. Which marked element sits in Group 12?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "Mo", "name": "molybdenum", "column": 6}, {"symbol": "Cd", "name": "cadmium", "column": 12}, {"symbol": "Tl", "name": "thallium", "column": 13}, … · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown; the shaded cells sit in the columns labeled 6 (molybdenum), 12…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCells": [
   {
    "symbol": "Mo",
    "name": "molybdenum",
    "column": 6
   },
   {
    "symbol": "Cd",
    "name": "cadmium",
    "column": 12
   },
   {
    "symbol": "Tl",
    "name": "thallium",
    "column": 13
   },
   {
    "symbol": "Kr",
    "name": "krypton",
    "column": 18
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown; the shaded cells sit in the columns labeled 6 (molybdenum), 12 (cadmium), 13 (thallium), and 18 (krypton)"
 }
}
Cadmium. KEY
Thallium.
Molybdenum.
Krypton.
PTB-003 · medium · application · seq 8 · authored | LOOP-1 PATCH: arsenic/antimony -> ruthenium/osmium (arsenic is a MATERIALS word owned by the seq-9 form-D item and sat adjacent to the seq-7 arsenic cell; Ru 1844 / Os 1803, era-valid group-8 behave-alike pair) · mcq4
Ruthenium and osmium behave alike. In a table built by Mendeleev's method, where do the two elements belong?
In the same column, each in its own row. KEY
Next to each other in the same row.
At opposite ends of the table.
In a single shared cell, since the table has room for only one of them.
PTB-001 · medium · application · seq 9 · authored | LOOP-1 REWRITE: old set zirconium/selenium/mercury/titanium put the MATERIALS words mercury (owner: seq-7 form-E) and titanium (owner: seq-8 form-B pair) on form C; new set yttrium/selenium/zirconium/rhenium keys Zr+Y (row 5). Zirconium also anchors the form-C seq-11 key - same form, non-adjacent, different drawn axis (row here, column there) - recorded for the blind telegraph screen · mcq4
The periodic table outline is shown with four cells marked: yttrium, selenium, zirconium, and rhenium. Which pair of marked elements is in the same period?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Y", "name": "yttrium", "row": 5, "column": 3}, {"symbol": "Se", "name": "selenium", "row": 4, "column": 16}, {"symbol": "Zr", "name": "zirconium… · columnPositionNote: "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled" · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
raw spec
{
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  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Y",
    "name": "yttrium",
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    "column": 3
   },
   {
    "symbol": "Se",
    "name": "selenium",
    "row": 4,
    "column": 16
   },
   {
    "symbol": "Zr",
    "name": "zirconium",
    "row": 5,
    "column": 4
   },
   {
    "symbol": "Re",
    "name": "rhenium",
    "row": 6,
    "column": 7
   }
  ],
  "columnPositionNote": "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled",
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
 }
}
Zirconium and yttrium KEY
Yttrium and selenium
Zirconium and rhenium
Selenium and rhenium
PTB-005 · medium · application · seq 10 · authored (list-comparison-audit rotation per the blueprint seq-10 contract: {hand-swaps-kept-but-named, detached-block confusion, better-mass-precision re-worded} — all PTB-005 fluency-recorded misconception classes; key invariant; no named pair, no digits) · mcq4
Before adopting the atomic-number list, chemists compared it against the old mass-ordered table. What did the comparison show that won them over?
The few pairs that mass order had misplaced now sat in columns matching their behavior, with no hand swaps left. KEY
The misfit pairs still had to be swapped by hand, but the new list gave those swaps an official name.
The misfit pairs had been moved out of the main table into a detached block printed underneath.
The atomic masses in the new list had been re-measured, so the old mass order came out corrected.
PTB-002 · medium · application · seq 11 · authored (element-choice middle-block case, target Group 4: key zirconium col 4 row 5; skip-block trap carbon col 14 - the fourth TALL column (carbon = PTB-001 rule-line period instance, non-key other-axis WARN recorded); row-read trap zinc row 4; right-edge trap antimony col 15 - the fourth column in from the right) | LOOP-1 PATCH: zinc -> yttrium (col 3): zinc is a MATERIALS word owned by the seq-7 form-B key; the row-read trap class is replaced by the one-column-left class (yttrium col 3 vs target 4), keeping three distinct trap classes. Yttrium also sits in the form-C seq-9 figure - same form, non-adjacent, different drawn axis - recorded for the blind screen. · mcq4
Four cells are marked on the periodic table outline: zirconium, carbon, yttrium, and antimony. Which marked element is in Group 4?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "Zr", "name": "zirconium", "column": 4, "row": 5}, {"symbol": "C", "name": "carbon", "column": 14, "row": 2}, {"symbol": "Y", "name": "yttrium", … · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown"
raw spec
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   {
    "symbol": "Zr",
    "name": "zirconium",
    "column": 4,
    "row": 5
   },
   {
    "symbol": "C",
    "name": "carbon",
    "column": 14,
    "row": 2
   },
   {
    "symbol": "Y",
    "name": "yttrium",
    "column": 3,
    "row": 5
   },
   {
    "symbol": "Sb",
    "name": "antimony",
    "column": 15,
    "row": 5
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown"
 }
}
Zirconium. KEY
Carbon.
Yttrium.
Antimony.
PTB-006 · medium · application · seq 12 · authored (LOOP-1 RE-INSTANCE: tin/lead are MATERIALS words owned by the form-A seeds at seqs 2/11 and 32/50/82 were shared numbers; instance = niobium/tantalum, consecutive group-5 members - NUMBERLESS stem (41 is owned by the form-E seq-19 item); one-metal confusion surface, historically true; distractor classes: same-ROW placement / mass-similarity / early-stretch-only-reach) · mcq4
For decades, chemists treated niobium and tantalum as a single metal: the two are so alike that samples of one were mistaken for the other, and their compounds follow matching recipes. In the atomic-number list the two sit far apart. What does the periodic law make of this pairing?
A return of the pattern: the law brings similar behavior back at regular intervals along the whole list, and the pair stacks into one column. KEY
The law explains the match by cutting the line so that niobium and tantalum land together in the same row of the table.
The likeness shows the two atomic masses must be nearly equal — under the law, matching behavior means matching mass.
The law runs out after the early stretch of the list, so a match between elements this far along is outside anything the law describes.
PTB-003 · medium · application · seq 13 · authored (blueprint's column-mismatch framing; element-free, digit-free) · mcq4
A chemist laying element cards in order of increasing atomic mass sees that keeping the current row going would put the next card under an element it does not resemble. The card's element acts just like the element that opened the row. What does the method call for?
Break the row: the card starts a new row, in the same column as the element it acts like. KEY
Keep the row going anyway, because the mass order fixes each card's spot in the row.
Set the card out of mass order, next to the element it acts like.
Hold every row to exactly the same length, breaking the line only when it reaches the set count.
PTB-007 · medium · application · seq 14 · authored (polarity flip — which version NEEDED the hand swap; letter-element relational surface, letters M/T claimed) | LOOP-1 PATCH: letters M/T -> D/G (the gram "M's atomic mass" collided cross-seq with the form-E seq-15 and seq-18 letter items). · mcq4
Element D's atomic mass is larger than element G's, yet D sits before G in the modern table. Which version of the table could seat this pair correctly only with a hand swap, and why?
The mass-ordered table — by mass G would come first, and only a hand swap kept the pair in columns matching its behavior. KEY
The atomic-number table — under atomic-number order the pair sat backward, and only a hand swap could set it right.
Both versions — every version of the table needs a few hand swaps to keep its columns lined up.
Neither version — the two orderings agree on this pair, so no swap was ever needed.
PTB-005 · medium · application · seq 15 · authored (evidence-completion surface, pool-12 letter-element class: position given in the stem, pick the additional fact that completes the disproof; letters J/L are non-symbol, disjoint from pool 12's Q/R) | LOOP-1 PATCH: the three quantity options rephrased ('Of the two, J is the heavier element.' etc.) - the original letter-carrying comparison grams collided with the form-B seq-14 stem/key, which uses the same J/L letters. | sol-loop-2: d2 flipped from the necessarily-true atomic-number fact to its ordering-impossible negation (cleanly false, same misconception territory). · mcq4
In the modern periodic table, element J comes immediately before element L. A student claims the table's order is set by atomic mass, from lightest to heaviest. Which additional fact about J and L would show the claim is wrong?
Of the two, J is the heavier element. KEY
Of the two, J is the lighter element.
Of the two atomic numbers, J's is the larger.
J was discovered many years before L.
PTB-007 · medium · application · seq 16 · authored (evidence->change case: the post-reordering observation is given; foils = wrong-change gaps / founding column design / fluency-1's rows-removed shape family) · mcq4
When the elements were relisted by atomic number, the pairs that mass order had misplaced fell into columns matching their behavior, and the hand swaps vanished. Which change in the table's story did this evidence carry?
The switch from mass ordering to atomic-number ordering. KEY
The decision to leave gaps for elements not yet discovered.
The grouping of similar elements into shared columns.
The removal of the rows so all elements sat in one line.
PTB-004 · hard · transfer · seq 17 · authored (TEST-IT-COULD-FAIL rotation per the blueprint seq-17 contract; foils = more-gaps-as-defeat (fluency-1 gap-as-error family), gap-match-confirms re-worded, prediction-timing-as-flaw (fluency-2 guesswork family); key invariant; elementless, no digits) · mcq4
By writing predictions for his empty cells, Mendeleev gave the table a test it could fail. Which later result would have failed that test?
An element finally found for a gap, with properties different from those predicted for it. KEY
Chemists finding more places where the mass order and the columns disagreed, and opening new gaps there.
A newly found element showing exactly the properties written down in advance for its empty cell.
The written predictions coming years before any of the missing elements were found.
PTB-005 · hard · transfer · seq 18 · authored (comes-LATER rotation per the blueprint seq-18 contract: fresh letters J/L, larger atomic number sits later; distractors {mass-order heavier-later (structural foil), hand-swap re-worded, re-measure/mass-blame} — PTB-005 gate/fluency-recorded classes; no real elements, no digits) · mcq4
Element J has a smaller atomic mass than element L, but a larger atomic number. Which element sits later in the modern periodic table's list?
J, because the list runs by increasing atomic number, and J's is larger. KEY
L, because the heavier element always sits later in the list.
Neither position is fixed — a pair like this must be swapped into place by hand.
The pair cannot be listed until its atomic masses are re-measured.
PTB-006 · hard · transfer · seq 19 · authored (numbering-error-claim rotation; LOOP-1 RE-INSTANCE: copper/silver are MATERIALS words owned by the row02 form-D item and the form-A seq-5 seed, and 47 was a shared number; instance = rubidium 37 / cesium 55, a genuinely behave-alike group-1 pair that appears in NO scope lesson's corpus - sole owner of the digits 37/55; foils = accept-error / coincidence-fallback / mass-similarity) | sol-loop-2: capitalized copper/silver feedback leftover swept (QB 3.9 class). · mcq4
Rubidium is element 37 and cesium is element 55, and the two behave alike. A student says one of the two atomic numbers must have been recorded wrong. What does the periodic law call the match?
One instance of the repeating pattern that runs through the atomic-number list. KEY
Evidence that one of the two atomic numbers is wrong.
A coincidence — with more than a hundred elements, some pairs are bound to match by chance.
A sign that rubidium and cesium have almost the same atomic mass.
PTB-007 · hard · transfer · seq 20 · authored (HAND-SWAP PRIORITY claim judgment: what the swaps reveal about mass vs behavior inside the mass-ordered table; foils = stayed-at-mass-positions flipped-record / swaps-held-the-gaps crossed-problems / masses-mismeasured wrong-reason) · mcq4
A textbook reviewer claims the hand swaps in Mendeleev's table show that he trusted atomic mass more than chemical behavior. Judge the claim against the historical record.
The claim is wrong — each swap set mass order aside to seat a pair by its behavior, so behavior won when the two disagreed. KEY
The claim is right — whenever mass and behavior disagreed about a pair, both elements stayed at their mass positions.
The claim is right — the swaps existed to hold the gaps in their predicted places until the missing elements arrived.
The claim is wrong, because the atomic masses of the swapped pairs had simply been measured incorrectly.
PTB-004 · medium · application · seq 21 · authored (blueprint rows[20] gap-prediction FRQ; letter-element column fragment: hard gray metals D/L, partner Z, recipe two-to-three, TWO-property rotation, melting falls down the column) | sol-loop-2: the steady column trend is now a STATED premise (two endpoint values alone underdetermine the in-between prediction; PTB-004 supplies no interpolation rule, so the scenario supplies the trend). · frq
Partway through assembling a Mendeleev-style table, a chemist sees that the next known element does not match the column where the mass order would place it, and leaves that cell empty. The column fragment reads, top to bottom: Element D, directly above the empty cell — a hard, gray metal; melts only in the hottest part of a furnace; its compound with element Z holds two atoms of D for every three atoms of Z. (the empty cell) Element L, directly below the empty cell — a hard, gray metal; melts at a noticeably lower temperature than D; its compound with element Z holds two atoms of L for every three atoms of Z. Down this column of the table, each of these properties changes steadily from one cell to the next.
Partway through assembling a Mendeleev-style table, a chemist sees that the next known element does not match the column where the mass order would place it, and leaves that cell empty. The column fragment reads, top to bottom: Element D, directly above the empty cell — a hard, gray metal; melts only in the hottest part of a furnace; its compound with element Z holds two atoms of D for every three atoms of Z. (the empty cell) Element L, directly below the empty cell — a hard, gray metal; melts at a noticeably lower temperature than D; its compound with element Z holds two atoms of L for every three atoms of Z. Down this column of the table, each of these properties changes steadily from one cell to the next. (a) The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now. (b) Predict each of the missing element's properties: the recipe of its compound with element Z, and its melting behavior. Justify both predictions by pointing to the properties of element D and element L. (c) Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Part a. The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now.
Model: The method allows her to write the missing element's predicted properties, read from the elements around the gap — here, from element D above and element L below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured.
Part b. Predict each of the missing element's properties: the recipe of its compound with element Z, and its melting behavior. Justify both predictions by pointing to the properties of element D and element L.
Model: Compound recipe with Z: two atoms of the missing element for every three atoms of Z — element D and element L both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — it should melt at a lower temperature than D but a higher temperature than L, because melting drops from D down to L and the missing element sits between them. Neither value is copied from either neighbor: D and L set the pattern, and the prediction continues it.
Part c. Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Model: To confirm: the discovered element's measured properties must match the written predictions — the two-atoms-to-three-atoms recipe with Z and melting between L's and D's. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with Z, or melting outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.
Full model answer. (a) The method allows her to write the missing element's predicted properties, read from the elements around the gap — here, from element D above and element L below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured. (b) Compound recipe with Z: two atoms of the missing element for every three atoms of Z — element D and element L both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — it should melt at a lower temperature than D but a higher temperature than L, because melting drops from D down to L and the missing element sits between them. Neither value is copied from either neighbor: D and L set the pattern, and the prediction continues it. (c) To confirm: the discovered element's measured properties must match the written predictions — the two-atoms-to-three-atoms recipe with Z and melting between L's and D's. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with Z, or melting outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.

Form D

PTB-001 · easy · recall · seq 1 · authored (James's PTB-001 figure-read structure kept verbatim-parallel; fresh instance: yttrium - spec-clean, non-MATERIALS, left edge of the middle block; loop-1 patch swapped ruthenium -> yttrium to free 'ruthenium's cell marked' for the row11 form-B statement item) · numeric
The periodic table outline is shown with yttrium's cell marked. Which period is yttrium in?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCell: {"symbol": "Y", "name": "yttrium", "row": 5} · style: "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 5, at the left edge of the t…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCell": {
   "symbol": "Y",
   "name": "yttrium",
   "row": 5
  },
  "style": "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 5, at the left edge of the table's middle block"
 }
}
Answer: 5 period KEY
also accepted: period 5, Period 5, 5.0
wrongValueDiagnostics
[
 {
  "value": 3,
  "misconception": "you counted columns across — yttrium's cell sits in the third column, but the period is the row",
  "feedback": "This answer is wrong — 3 comes from counting columns across. Yttrium's cell sits in the third column, but the period is the row. Counting rows from the top, yttrium's cell sits in row 5, so yttrium is in Period 5."
 }
]
feedback
{
 "keyExplanation": "Find the row that holds the marked cell. Counting from the top, yttrium's cell sits in row 5. Yttrium is in Period 5.",
 "anticipatedWrong": [
  {
   "value": 3,
   "misconception": "you counted columns across — yttrium's cell sits in the third column, but the period is the row",
   "feedback": "This answer is wrong — 3 comes from counting columns across. Yttrium's cell sits in the third column, but the period is the row. Counting rows from the top, yttrium's cell sits in row 5, so yttrium is in Period 5."
  }
 ]
}
PTB-002 · easy · recall · seq 2 · authored (James's PTB-002 figure-read structure kept verbatim-parallel; fresh instance: copper, classroom-set rule; middle-block cell so only the row-read trap has a defined value - manganese fluency class, single diagnostic like the pool[4] seed) · numeric
The periodic table outline is shown with copper's cell marked. Which group is copper in?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Cu", "name": "copper"} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Cu",
   "name": "copper"
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Answer: 11 group KEY
also accepted: group 11, Group 11, 11.0
wrongValueDiagnostics
[
 {
  "value": 4,
  "misconception": "you read the row number — copper sits in row 4, but the group is the column",
  "feedback": "This answer is wrong — 4 is the row number. Copper sits in row 4, but the group is the column its cell sits in. The middle-block columns have numbers of their own: copper's cell sits in column 11, so copper is in Group 11."
 }
]
feedback
{
 "keyExplanation": "Find the column that holds the marked cell. Copper sits in the middle block, and those columns have numbers of their own — its column is the eleventh from the left. Copper is in Group 11.",
 "anticipatedWrong": [
  {
   "value": 4,
   "misconception": "you read the row number — copper sits in row 4, but the group is the column",
   "feedback": "This answer is wrong — 4 is the row number. Copper sits in row 4, but the group is the column its cell sits in. The middle-block columns have numbers of their own: copper's cell sits in column 11, so copper is in Group 11."
  }
 ]
}
PTB-003 · easy · recall · seq 3 · authored (cards case rotated onto a redo-the-sort surface; element-free, digit-free) | sol-loop-2: d2 rationale corrected (color/state ARE recorded physical properties; the failure is that alone they cannot order the cards) - the old wording said looks 'played no part', contradicting PTB-003's similar chemical AND physical properties. · mcq4
A chemist in Mendeleev's day sets out to repeat the card sort. What must each element's card show for the method to work?
Its atomic mass and the properties chemists had already recorded for it. KEY
Its atomic number, taken from a count of the protons in its atoms.
Its color and its usual state, the two things easiest to see at a glance.
Only its name, since the sorting itself would supply everything else.
PTB-006 · easy · recall · seq 4 · authored (ordering-case rotation per the blueprint seq-4 contract: {mass ordering re-worded, discovery order, metals-first single-property split}; key invariant — the taught required ordering) · mcq4
A student wants to arrange the elements so that the periodic law's pattern appears. How should the elements be ordered?
In order of increasing atomic number. KEY
From lightest atomic mass to heaviest.
In the order in which the elements were discovered.
With the metals listed first, then the nonmetals.
PTB-001 · medium · application · seq 5 · authored (James's PTB-001 four-cell period-read structure kept verbatim-parallel; fresh set boron/krypton/antimony/osmium - four distinct rows 2/4/5/6, the widest spread of any form, with a one-row-too-low trap directly under the key) · mcq4
The periodic table outline is shown with four cells marked: boron, krypton, antimony, and osmium. Which marked element sits in Period 4?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "B", "name": "boron", "row": 2}, {"symbol": "Kr", "name": "krypton", "row": 4}, {"symbol": "Sb", "name": "antimony", "row": 5}, {"symbol": "Os", … · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 2 (boron), 4 (krypton)…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "B",
    "name": "boron",
    "row": 2
   },
   {
    "symbol": "Kr",
    "name": "krypton",
    "row": 4
   },
   {
    "symbol": "Sb",
    "name": "antimony",
    "row": 5
   },
   {
    "symbol": "Os",
    "name": "osmium",
    "row": 6
   }
  ],
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 2 (boron), 4 (krypton), 5 (antimony), and 6 (osmium)"
 }
}
Krypton. KEY
Antimony.
Boron.
Osmium.
PTB-004 · medium · application · seq 6 · authored (LICENSE case, fresh surface vs the pool[9] form-A seed; foils = pool[9]'s need-a-sample + copy-the-neighbor families and fluency-2's average-the-table family) · mcq4
Following Mendeleev's gap method, a chemist writes an atomic mass and a density beside an empty cell in the table — before anyone has ever seen the missing element. What kind of values is she writing down?
Predictions read from the elements around the gap. KEY
Measurements taken from a first small sample of the element.
The values of the element just above the gap, copied unchanged.
Averages of the values of every element known at the time.
PTB-002 · medium · application · seq 7 · authored (seed-parallel marked-set rotation: vanadium/chromium/platinum/selenium, key chromium Group 6; far-cell slot upgraded to the taught skip-the-middle-block misconception — selenium's column 16 reads as 'the sixth' only when the ten middle-block columns are skipped) · mcq4
The periodic table outline is shown with four cells marked: vanadium, chromium, platinum, and selenium. Which marked element sits in Group 6?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "V", "name": "vanadium", "column": 5}, {"symbol": "Cr", "name": "chromium", "column": 6}, {"symbol": "Pt", "name": "platinum", "column": 10}, {"s… · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — vanadium's cell in column 5, chromium's in column 6, platinum…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCells": [
   {
    "symbol": "V",
    "name": "vanadium",
    "column": 5
   },
   {
    "symbol": "Cr",
    "name": "chromium",
    "column": 6
   },
   {
    "symbol": "Pt",
    "name": "platinum",
    "column": 10
   },
   {
    "symbol": "Se",
    "name": "selenium",
    "column": 16
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — vanadium's cell in column 5, chromium's in column 6, platinum's in column 10, selenium's in column 16"
 }
}
Chromium. KEY
Vanadium.
Platinum.
Selenium.
PTB-003 · medium · application · seq 8 · authored | LOOP-1 PATCH: palladium/platinum -> rhodium/iridium (platinum is a MATERIALS word owned by the seq-7 form-D cell and sat adjacent at seqs 7/8; Rh/Ir 1803, era-valid group-9 behave-alike pair); stem rephrased off the PTB-003 article's own 'method put(s)' wording (v1 spec-text gram) · mcq4
Rhodium and iridium behave alike, even though their atomic masses are far apart. Where do they belong in a table built by Mendeleev's method?
In the same column, one above the other. KEY
Next to each other in the same row.
At opposite ends of the table, because their masses are far apart.
Together in one cell, because the table has room for only one of them.
PTB-001 · medium · application · seq 9 · authored | LOOP-1 REWRITE: old set arsenic/bismuth/chromium/palladium put chromium (MATERIALS, owner: seq-7 form-D key - same form AND cross-form collisions) in the set; new set arsenic/palladium/bismuth/thallium keys Bi+Tl (row 6) with a shared-column trap (As and Bi both in column 15); arsenic keeps its single MATERIALS slot here · mcq4
The periodic table outline is shown with four cells marked: arsenic, palladium, bismuth, and thallium. Which pair of marked elements is in the same period?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "As", "name": "arsenic", "row": 4, "column": 15}, {"symbol": "Pd", "name": "palladium", "row": 5, "column": 10}, {"symbol": "Bi", "name": "bismut… · columnPositionNote: "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled" · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "As",
    "name": "arsenic",
    "row": 4,
    "column": 15
   },
   {
    "symbol": "Pd",
    "name": "palladium",
    "row": 5,
    "column": 10
   },
   {
    "symbol": "Bi",
    "name": "bismuth",
    "row": 6,
    "column": 15
   },
   {
    "symbol": "Tl",
    "name": "thallium",
    "row": 6,
    "column": 13
   }
  ],
  "columnPositionNote": "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled",
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
 }
}
Bismuth and thallium KEY
Arsenic and bismuth
Palladium and bismuth
Arsenic and palladium
PTB-005 · medium · application · seq 10 · authored (why-replace-an-almost-right-order rotation per the blueprint seq-10 contract: {tie-breaker-only demotion of atomic number, authority re-worded, masses-measured-wrong blame}; key invariant; no named pair, no digits) · mcq4
Mass order had already placed most elements correctly. Why did chemists still replace it with atomic-number order?
Atomic-number order also fixed the misfit pairs — every element landed in a behavior-matching column, with no hand swaps. KEY
The close-mass pairs counted as ties, and atomic number was adopted only as the agreed tie-breaker between them.
Chemists deferred to Moseley's scientific standing and adopted whatever order he proposed.
The atomic masses of the misfit pairs turned out to have been measured wrong.
PTB-002 · medium · application · seq 11 · authored (statement-choice case, cadmium col 12 row 5 — a middle-block cell's group; no-number skip statement, row-read gives Group 5, one-column-short miscount gives Group 11) | LOOP-1 PATCH: stem clause 'is asked for' -> 'wants' (cross-seq gram vs the form-C seq-4 stem). · mcq4
The periodic table outline is shown with cadmium's cell marked. A student wants cadmium's group number. Which statement gets it right?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Cd", "name": "cadmium", "column": 12, "row": 5} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Cd",
   "name": "cadmium",
   "column": 12,
   "row": 5
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Cadmium is in Group 12 — counting every column from the left edge, middle block included, its cell sits in the twelfth column. KEY
Cadmium has no group number — only the tall columns on the left and right sides of the table are numbered, and cadmium's cell sits in the middle block.
Cadmium is in Group 5 — the group is the row a cell sits in, and cadmium's cell sits in the fifth row.
Cadmium is in Group 11 — counting from the left with the middle block included, its cell sits in the eleventh column.
PTB-006 · medium · application · seq 12 · authored (LOOP-1 RE-INSTANCE: silver/gold are MATERIALS words owned by the form-A seq-5 seed and the form-E seq-7 key, and 47/79/32 were shared numbers; instance = zirconium/hafnium, consecutive group-4 members - NUMBERLESS stem (72 is spec text of PTB-004); hidden-in-ores surface, historically true; distractor classes: fixed-8-universal-count / same-ROW placement / steady-drift) · mcq4
Zirconium and hafnium are so chemically alike that hafnium went undetected for years inside zirconium ores, and the two metals form compounds with matching recipes. The two sit far apart in the numbered list of elements. According to the periodic law, what does this observation show?
The pattern returning: the law promises look-alikes at regular intervals along the entire list, so zirconium and hafnium stack in the same column. KEY
Matches under the law come exactly every 8 elements, so two look-alike metals spaced this far apart cannot both belong to the pattern.
The law accounts for the match by cutting the line so that zirconium and hafnium land in the same row of the table.
Properties change steadily along the list with no repeats, so the law reads a match between two distant metals as a mistake in the reported behavior.
PTB-003 · medium · application · seq 13 · authored (element-free, digit-free) | sol-loop-2: categorical 'never changes/never reshuffled' scoped to the method's two rules (PTB-005/007 later teach the recorded hand swaps). · mcq4
Partway through a mass-ordered row of element cards, a chemist finds that the next card's element repeats the behavior of the element that began the row. Which move follows Mendeleev's method?
Starting a new row with that card, stacking it below the element whose behavior it repeats. KEY
Adding the card to the current row, since nothing in the layout says a row must ever end.
Reordering the nearby cards so the two behave-alike elements sit together in one row.
Counting the cards in the row and ending it only when it holds the usual number.
PTB-007 · medium · application · seq 14 · authored (hand-swap ledger read — what the reordering did to the swap list; element-free, digit-free) · mcq4
In the mass-ordered table, a chemist keeps a short list of element pairs whose places have to be traded by hand to match their behavior. What did the switch to ordering by atomic number do to that list?
It emptied the list — ordered by atomic number, every pair sits in columns matching its behavior, with no swaps. KEY
It lengthened the list — the new ordering created misfit pairs of its own.
It kept the list unchanged, but the swaps were renamed as an accepted, permanent part of the table's printed design.
It shortened the list to only the pairs whose atomic masses sit closest together.
PTB-005 · medium · application · seq 15 · authored (evidence-shape surface, instance-free: which KIND of observation could disprove the mass claim; no elements, no letters, no numbers) · mcq4
A student wants to test the claim that atomic mass decides each element's place in the modern periodic table. What kind of observation could show the claim is wrong?
A pair of elements in which the heavier one comes first in the table. KEY
A pair of elements in which the lighter one comes first in the table.
A stretch of the table where atomic mass grows from each cell to the next.
Two elements in one column that behave in similar ways.
PTB-007 · medium · application · seq 16 · authored (full two-evidence PAIRING case: both classes named in the stem, options pair each evidence to a change; foils = swapped pairing / both-to-one / merge-and-blame-the-columns) · mcq4
Two kinds of evidence run through the table's story: elements discovered to match gap predictions, and mass-misplaced pairs that settled into matching columns under the new ordering. Which pairing matches each evidence to the change it supported?
The confirmed predictions backed the original pattern; the settled pairs carried the reordering by atomic number. KEY
The settled pairs backed the original pattern; the confirmed predictions carried the reordering by atomic number.
Both kinds of evidence carried the reordering; the original pattern was accepted without evidence of its own.
The confirmed predictions showed that atomic number equals atomic mass; the settled pairs showed the columns were drawn wrong.
PTB-004 · hard · transfer · seq 17 · authored (JOURNAL-REPORT rotation per the blueprint seq-17 contract; foils = fit-as-problem re-worded, more-gaps-as-defeat re-worded, design-as-flaw re-worded; key invariant; elementless, no digits) | LOOP-2 PATCH (blind F2, r1): "evidence against the table" was ambiguous between the pattern and the mass ordering, making the fresh-mismatch distractor defensible; the stem now targets trusting the table's PREDICTIONS and the distractor states the method-working reading explicitly. | sol-loop-5: key no longer echoes the stem's 'predictions' wording ('broke the prediction' -> concrete written-for-its-cell mismatch), removing the definition-in-key clang. · mcq4
In the years after Mendeleev's table appeared, chemists sent reports of new findings to the journals. Which report, if confirmed, would have been evidence against trusting the table's predictions?
A report that a gap element had been found whose measured properties were nothing like what had been written for its cell. KEY
A report that a just-discovered element matched the behavior of a column already in the table.
A report that the next element in the mass order had not matched its column's properties, so a fresh gap had been marked out partway down the table.
A report that two elements sharing a column also shared their chemical behavior.
PTB-005 · hard · transfer · seq 18 · authored (close-mass pick rotation per the blueprint seq-18 contract: fresh letters T/E, first-named element keys; distractors {mass-order re-worded (structural foil), tie-rule re-worded, discovery-date} — PTB-005 fluency-recorded classes; no real elements, no digits) · mcq4
Elements T and E have nearly equal atomic masses, with T's a little larger. T's atomic number is smaller than E's. Which element does the modern periodic table list first?
T, because the smaller atomic number always comes first in the modern table. KEY
E, because its atomic mass is the smaller of the two.
Masses this close count as a tie, so either element may be printed first in the table.
Whichever of the two was discovered first comes first.
PTB-006 · hard · transfer · seq 19 · authored (stops-early-claim rotation; LOOP-1 RE-INSTANCE: tin/lead are MATERIALS words owned by the form-A seeds at seqs 2/11 and 32/50/82 were shared numbers; instance = niobium/tantalum, NUMBERLESS - the group-5 pair is the only clean same-group pair left on form D; question clause aligned to the seq-19 sibling 'call the match' off the PTB-006 article's own 'law say' wording; foils = accept-stops-early / fixed-at-8 / mass-similarity) | sol-loop-2: capitalized tin/lead feedback leftover swept (QB 3.9 class). · mcq4
Niobium and tantalum sit far apart in the atomic-number list, and the two behave alike. A classmate says the repeating pattern only holds for the early elements, so a match this far along the list must be chance. What does the periodic law call the match?
One more repeat of the pattern — the intervals grow longer, but the repeating never stops. KEY
The pattern really has run out that far along the list, so the match is just chance.
The match cannot be the law's work, because the two sit far more than 8 places apart.
The two behave alike only because their atomic masses are nearly equal.
PTB-007 · hard · transfer · seq 20 · authored (PREDICTIONS-AS-LUCK claim judgment: method vs chance for the gap predictions; foils = written-after-discoveries reversed-timeline / method-said-nothing erased-method / reordering-confirmed-them wrong-chapter wrong-reason) · mcq4
A student claims that Mendeleev's successful predictions for the gaps were lucky guesses. Judge the claim against the historical record.
The claim is wrong — the predictions were read from the elements around each gap, and later discoveries matched them. KEY
The claim is right — the predictions were only written down after the matching elements had been discovered.
The claim is right — the method never said what a missing element should be like, so any match was chance.
The claim is wrong, because it was the reordering by atomic number that finally confirmed the predictions.
PTB-004 · medium · application · seq 21 · authored (blueprint rows[20] gap-prediction FRQ; letter-element column fragment: brittle dark solids T/X, partner G, recipe one-to-three, TWO-property rotation, reaction vigor rises down the column) | sol-loop-2: the steady column trend is now a STATED premise (two endpoint values alone underdetermine the in-between prediction; PTB-004 supplies no interpolation rule, so the scenario supplies the trend). · frq
A chemist reaches a spot in the mass order where the next known element fails to match the column's properties, and leaves the cell empty rather than force the element in. The column reads, top to bottom: Element T, directly above the empty cell — a brittle, dark solid; reacts with element G only when strongly heated; its compound with element G holds one atom of T for every three atoms of G. (the empty cell) Element X, directly below the empty cell — a brittle, dark solid; reacts briskly with element G even without heating; its compound with element G holds one atom of X for every three atoms of G. Down this column of the table, each of these properties changes steadily from one cell to the next.
A chemist reaches a spot in the mass order where the next known element fails to match the column's properties, and leaves the cell empty rather than force the element in. The column reads, top to bottom: Element T, directly above the empty cell — a brittle, dark solid; reacts with element G only when strongly heated; its compound with element G holds one atom of T for every three atoms of G. (the empty cell) Element X, directly below the empty cell — a brittle, dark solid; reacts briskly with element G even without heating; its compound with element G holds one atom of X for every three atoms of G. Down this column of the table, each of these properties changes steadily from one cell to the next. (a) The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now. (b) Predict each of the missing element's properties: the recipe of its compound with element G, and how readily it reacts with element G. Justify both predictions by pointing to the properties of element T and element X. (c) Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Part a. The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now.
Model: The method allows him to write the missing element's predicted properties, read from the elements around the gap — here, from element T above and element X below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured.
Part b. Predict each of the missing element's properties: the recipe of its compound with element G, and how readily it reacts with element G. Justify both predictions by pointing to the properties of element T and element X.
Model: Compound recipe with G: one atom of the missing element for every three atoms of G — element T and element X both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Reaction vigor with G: in between its neighbors — it should react more readily than T but less readily than X, for example under gentle heating: T needs strong heating, X needs none, and the missing element sits between them, so its vigor must continue that step-by-step climb. Neither value is copied from either neighbor: T and X set the pattern, and the prediction continues it.
Part c. Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Model: To confirm: the discovered element's measured properties must match the written predictions — the one-atom-to-three-atoms recipe with G and reaction vigor between T's and X's. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with G, or vigor outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.
Full model answer. (a) The method allows him to write the missing element's predicted properties, read from the elements around the gap — here, from element T above and element X below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured. (b) Compound recipe with G: one atom of the missing element for every three atoms of G — element T and element X both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Reaction vigor with G: in between its neighbors — it should react more readily than T but less readily than X, for example under gentle heating: T needs strong heating, X needs none, and the missing element sits between them, so its vigor must continue that step-by-step climb. Neither value is copied from either neighbor: T and X set the pattern, and the prediction continues it. (c) To confirm: the discovered element's measured properties must match the written predictions — the one-atom-to-three-atoms recipe with G and reaction vigor between T's and X's. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with G, or vigor outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.

Form E

PTB-001 · easy · recall · seq 1 · authored (James's PTB-001 figure-read structure kept verbatim-parallel; fresh instance: thallium - spec-clean, non-MATERIALS; its column (13) reproduces the gallium seed's own 13-column misread value with a fresh element) · numeric
The periodic table outline is shown with thallium's cell marked. Which period is thallium in?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCell: {"symbol": "Tl", "name": "thallium", "row": 6} · style: "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 6, in the first column after…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCell": {
   "symbol": "Tl",
   "name": "thallium",
   "row": 6
  },
  "style": "plain outline, period numbers 1-7 down the left, one cell shaded with its symbol shown; the shaded cell sits in the row labeled 6, in the first column after the table's middle block"
 }
}
Answer: 6 period KEY
also accepted: period 6, Period 6, 6.0
wrongValueDiagnostics
[
 {
  "value": 13,
  "misconception": "you counted columns across — thallium's cell sits in the thirteenth column, but the period is the row",
  "feedback": "This answer is wrong — 13 comes from counting columns across. Thallium's cell sits in the thirteenth column, but the period is the row. Counting rows from the top, thallium's cell sits in row 6, so thallium is in Period 6."
 }
]
feedback
{
 "keyExplanation": "Find the row that holds the marked cell. Counting from the top, thallium's cell sits in row 6. Thallium is in Period 6.",
 "anticipatedWrong": [
  {
   "value": 13,
   "misconception": "you counted columns across — thallium's cell sits in the thirteenth column, but the period is the row",
   "feedback": "This answer is wrong — 13 comes from counting columns across. Thallium's cell sits in the thirteenth column, but the period is the row. Counting rows from the top, thallium's cell sits in row 6, so thallium is in Period 6."
  }
 ]
}
PTB-002 · easy · recall · seq 2 · authored (James's PTB-002 figure-read structure kept verbatim-parallel; fresh instance: rhodium - spec-clean, non-MATERIALS, middle-block cell so only the row-read trap has a defined value - manganese fluency class, single diagnostic like the pool[4] seed; loop-1 patch swapped zinc -> rhodium: zinc is a MATERIALS word whose single validator-legal slot is the row07 form-B KEY, and cadmium was blocked by the row11 form-D single-cell stem) · numeric
The periodic table outline is shown with rhodium's cell marked. Which group is rhodium in?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Rh", "name": "rhodium"} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Rh",
   "name": "rhodium"
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Answer: 9 group KEY
also accepted: group 9, Group 9, 9.0
wrongValueDiagnostics
[
 {
  "value": 5,
  "misconception": "you read the row number — rhodium sits in row 5, but the group is the column",
  "feedback": "This answer is wrong — 5 is the row number. Rhodium sits in row 5, but the group is the column its cell sits in. The middle-block columns have numbers of their own: rhodium's cell sits in column 9, so rhodium is in Group 9."
 }
]
feedback
{
 "keyExplanation": "Find the column that holds the marked cell. Rhodium sits in the middle block, and those columns have numbers of their own — its column is the ninth from the left. Rhodium is in Group 9.",
 "anticipatedWrong": [
  {
   "value": 5,
   "misconception": "you read the row number — rhodium sits in row 5, but the group is the column",
   "feedback": "This answer is wrong — 5 is the row number. Rhodium sits in row 5, but the group is the column its cell sits in. The middle-block columns have numbers of their own: rhodium's cell sits in column 9, so rhodium is in Group 9."
  }
 ]
}
PTB-003 · easy · recall · seq 3 · authored (rules case rotated onto a role-attribution surface; key anchored on the lesson's canonical order-vs-row-breaks wording; element-free, digit-free) · mcq4
Mendeleev's method needed two facts about every element: the atomic mass, and the way the element behaves. What job did each fact do?
The atomic mass set the order along the line, and the behavior set where each row ended. KEY
The behavior set the order along the line, and the atomic mass set where each row ended.
The atomic mass set the order along the line, and each row ended after a fixed count of elements.
The atomic number set the order along the line, and the behavior set where each row ended.
PTB-006 · easy · recall · seq 4 · authored (statement-case rotation per the blueprint seq-4 contract: {steady-drift re-worded, same-period similarity re-worded, no-pattern denial}; key sentence invariant — the taught fact) · mcq4
Your class is making a poster about the periodic law. Which sentence gives the law itself?
Listed in order of increasing atomic number, elements with similar properties appear at regular intervals. KEY
Moving from the first element in the list to the last, the properties drift steadily in one direction and never return.
Elements in the same period of the table share similar properties.
No single ordering makes the elements' properties form a pattern — each element behaves in its own way.
PTB-001 · medium · application · seq 5 · authored (James's PTB-001 four-cell period-read structure kept verbatim-parallel; fresh set selenium/yttrium/zirconium/iridium - key listed first like the seed; one-row-too-low trap plus a second row-5 cell and a row-6 far cell) · mcq4
The periodic table outline is shown with four cells marked: selenium, yttrium, zirconium, and iridium. Which marked element sits in Period 4?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Se", "name": "selenium", "row": 4}, {"symbol": "Y", "name": "yttrium", "row": 5}, {"symbol": "Zr", "name": "zirconium", "row": 5}, {"symbol": "I… · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 4 (selenium), 5 (yttri…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Se",
    "name": "selenium",
    "row": 4
   },
   {
    "symbol": "Y",
    "name": "yttrium",
    "row": 5
   },
   {
    "symbol": "Zr",
    "name": "zirconium",
    "row": 5
   },
   {
    "symbol": "Ir",
    "name": "iridium",
    "row": 6
   }
  ],
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown; the shaded cells sit in the rows labeled 4 (selenium), 5 (yttrium and zirconium), and 6 (iridium)"
 }
}
Selenium. KEY
Yttrium.
Zirconium.
Iridium.
PTB-004 · medium · application · seq 6 · authored (STEPS case, next-step presentation vs the pool[11] form-B full ordering; foils = predict-first sequencing foil (REAL later step), pool[11]'s force-it-in family, fluency-1's deleted-element family) · mcq4
Working along the mass order, a chemist reaches the next known element and finds that its properties do not match the column where it would land. Under Mendeleev's gap method, what is the very next step?
Leave that cell empty instead of forcing the element in. KEY
Predict the missing element's properties from its neighbors.
Force the element into the column and note the mismatch for later.
Take the unmatched element out of the table altogether.
PTB-002 · medium · application · seq 7 · authored (seed-parallel marked-set rotation: tungsten/gold/mercury/bismuth, key gold Group 11; all four marked cells share one row, a straight left-to-right column sweep) | LOOP-1 PATCH: bismuth -> hafnium (column 4): the seq-8 form-E Mendeleev pair became antimony/bismuth (the only era-valid clean pair left on E), and bismuth may sit in one form-E item only. | sol-loop-2: style enumeration re-derived from the markedCells (loop-1 token swap left the OLD element's column on the swapped-in name - QB 3.9 leftover class, caught by sol). · mcq4
The periodic table outline is shown with four cells marked: hafnium, tungsten, gold, and mercury. Which marked element sits in Group 11?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCells: [{"symbol": "Hf", "name": "hafnium", "column": 4}, {"symbol": "W", "name": "tungsten", "column": 6}, {"symbol": "Au", "name": "gold", "column": 11}, {"symbol… · style: "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — hafnium's cell in column 4, tungsten's in column 6, gold's in…
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCells": [
   {
    "symbol": "Hf",
    "name": "hafnium",
    "column": 4
   },
   {
    "symbol": "W",
    "name": "tungsten",
    "column": 6
   },
   {
    "symbol": "Au",
    "name": "gold",
    "column": 11
   },
   {
    "symbol": "Hg",
    "name": "mercury",
    "column": 12
   }
  ],
  "style": "plain outline, group numbers 1-18 across the top, four cells shaded with their symbols shown — hafnium's cell in column 4, tungsten's in column 6, gold's in column 11, mercury's in column 12"
 }
}
Gold. KEY
Tungsten.
Mercury.
Hafnium.
PTB-003 · medium · application · seq 8 · authored | LOOP-1 PATCH: chromium/molybdenum -> antimony/bismuth (chromium is a MATERIALS word owned by the seq-7 form-D key; Sb/Bi known since antiquity, era-valid group-15 behave-alike pair - the only clean pair left on form E) · mcq4
Antimony and bismuth react in similar ways. According to Mendeleev's method, how do their places in his table compare?
They share a column, each in its own row. KEY
They sit side by side in the same row.
They sit at opposite ends of the table.
They occupy a single shared cell, because the table has room for only one of them.
PTB-001 · medium · application · seq 9 · authored | LOOP-1 REWRITE: old set krypton/thallium/copper/xenon put copper (MATERIALS, owner: row02 form-D) on form E, and thallium moved to the form-E seq-1 stem; new set krypton/tantalum/palladium/xenon keys Pd+Xe (row 5) with the krypton-above-xenon shared-column trap kept · mcq4
The periodic table outline is shown with four cells marked: krypton, tantalum, palladium, and xenon. Which pair of marked elements is in the same period?
FIGURE (periodic-table-rows · stimulus) — rowLabels: true · columnLabels: false · markedCells: [{"symbol": "Kr", "name": "krypton", "row": 4, "column": 18}, {"symbol": "Ta", "name": "tantalum", "row": 6, "column": 5}, {"symbol": "Pd", "name": "palladiu… · columnPositionNote: "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled" · style: "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-rows",
  "rowLabels": true,
  "columnLabels": false,
  "markedCells": [
   {
    "symbol": "Kr",
    "name": "krypton",
    "row": 4,
    "column": 18
   },
   {
    "symbol": "Ta",
    "name": "tantalum",
    "row": 6,
    "column": 5
   },
   {
    "symbol": "Pd",
    "name": "palladium",
    "row": 5,
    "column": 10
   },
   {
    "symbol": "Xe",
    "name": "xenon",
    "row": 5,
    "column": 18
   }
  ],
  "columnPositionNote": "column is the drawn horizontal cell position (1-18); column numbers are NOT printed on this outline — only the period numbers 1-7 down the left are labeled",
  "style": "plain outline, period numbers 1-7 down the left, four cells shaded with their symbols shown"
 }
}
Palladium and xenon KEY
Krypton and xenon
Krypton and palladium
Tantalum and xenon
PTB-005 · medium · application · seq 10 · authored (debate-settling-result rotation per the blueprint seq-10 contract: {hand-swaps-kept re-worded, detached-block confusion re-worded, tie-rule re-worded} — all PTB-005 fluency-recorded misconception classes; key invariant; no named pair, no digits) · mcq4
A chemistry club is debating why the table's ordering rule changed from atomic mass to atomic number. Which result settled the question for chemists at the time?
Every element ended up in a column that fit its behavior, and the pairs once swapped by hand no longer needed it. KEY
The stubborn pairs still sat against the ordering rule, so chemists went on correcting them by hand, just less often.
The pairs that broke the old order were parked in a separate block below the table so the main list stayed clean.
Chemists agreed that masses closer than one unit counted as a tie, with atomic number used only to break those ties.
PTB-002 · medium · application · seq 11 · authored (statement-choice case, molybdenum col 6 row 5 — a middle-block cell's group; no-number skip statement, row-read gives Group 5, one-column-far miscount gives Group 7 — 'is in Group 7' gram rides the Mn fluency scaffold whitelist source, number 7 <= 12) · mcq4
The periodic table outline is shown with molybdenum's cell marked. Which statement about molybdenum's group is correct?
FIGURE (periodic-table-columns · stimulus) — columnLabels: true · rowLabels: false · markedCell: {"symbol": "Mo", "name": "molybdenum", "column": 6, "row": 5} · style: "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-columns",
  "columnLabels": true,
  "rowLabels": false,
  "markedCell": {
   "symbol": "Mo",
   "name": "molybdenum",
   "column": 6,
   "row": 5
  },
  "style": "plain outline, group numbers 1-18 across the top, one cell shaded with its symbol shown"
 }
}
Molybdenum is in Group 6 — counting from the left edge and including the ten middle-block columns, its cell sits in the sixth column. KEY
Molybdenum has no group number — group numbers belong only to the tall columns at the two sides of the table, and molybdenum's cell sits in the middle block.
Molybdenum is in Group 5 — its cell sits in the fifth row, and the group of an element is the row it occupies.
Molybdenum is in Group 7 — counting from the left with the middle block included, its cell sits in the seventh column.
PTB-006 · medium · application · seq 12 · authored (LOOP-1 RE-INSTANCE: the old antimony/bismuth pair moved to the seq-8 form-E Mendeleev item (the only era-valid clean pair left on E) and its 51/83 digits to the form-B sibling; instance = ruthenium/osmium, consecutive group-8 members - sole owner of the digits 44/76, interval left unstated; distractor classes: neighbor-adjacency-demand / mass-similarity / column-as-cause) · mcq4
Ruthenium (atomic number 44) and osmium (atomic number 76) are both dense, hard metals with very high melting points, and their compounds follow matching recipes. The two sit far apart when the elements are lined up by atomic number. How does the periodic law account for this likeness?
As a return of its repeating pattern: look-alikes recur at regular intervals through the whole list, so ruthenium and osmium stack in one column. KEY
The law seats elements that act alike right next to each other in the list, so ruthenium and osmium must be far out of position.
The likeness means the two atomic masses are nearly equal — under the law, elements act alike when their masses match.
The two act alike because the table seated them in one column; the numbered list of elements plays no part in the law's account.
PTB-003 · medium · application · seq 13 · authored (element-free, digit-free) · mcq4
A chemist working card by card in order of increasing atomic mass reaches a card whose element behaves just like the element at the head of the row being laid. What is the method's next move?
Beginning a new row with the card, seating it in the column of the element it behaves like. KEY
Continuing the current row, laying the card in the next position along the line.
Lifting the card out of the mass order and placing it beside its behave-alike partner.
Holding the row open until it matches the length of the row above, then starting the new row.
PTB-007 · medium · application · seq 14 · authored (two-renderings comparison — why the modern table needs no hand-swap note; element-free, digit-free) · mcq4
A history-of-chemistry poster shows the same stubborn element pair twice: in an old mass-ordered table its cells carry a hand-swap note, but in the modern table there is no note. Why does the modern table need no note for this pair?
It orders elements by atomic number, which seats the pair in columns matching its behavior — no patch needed. KEY
It quietly keeps the swap — modern tables simply stopped printing the note.
The pair's masses were re-measured, and the old mass order turned out to be right after all.
The two tables are really one and the same table drawn in two different styles, so the note was never needed at all.
PTB-005 · medium · application · seq 15 · authored (observation-selection surface, letter-element class: four complete observations, pick the disproving one; letters X/Z/M/T are non-symbol, disjoint from pool 12's Q/R and form C's J/L) | sol-loop-2: all-true declaration (the foils are true-but-non-disproving by the task's design). | sol-loop-3: the three true-but-irrelevant observations replaced with cleanly false claims (discovery-order / mass-revision / column-mass); stem reverted to the direct question (the X-Z reversal key is unchanged). | sol-loop-4: keyExplanation re-enumerated against the loop-3 options (stale M-before-T / growing-numbers references removed). · mcq4
A student claims the modern periodic table runs from the lightest element to the heaviest. Which fact shows the claim is wrong?
Element X comes before element Z, even though X's atomic mass is larger than Z's. KEY
Element M sits before element T only because M was discovered first.
An element's place in the list moves whenever its atomic mass is remeasured.
Elements M and T share a column, so their masses must nearly match.
PTB-007 · medium · application · seq 16 · authored (evidence->role case: the stubborn pairs under mass order; key tracks rule line 6; foils = crossed evidence classes / columns-drawn-wrong / elements-removed) · mcq4
Under the mass ordering, certain pairs of known elements kept landing in columns that did not match their behavior, and only hand swaps could fix them. What role did these stubborn pairs play in the table's story?
They forced the change from mass ordering to atomic-number ordering. KEY
They confirmed the properties that had been predicted for the gaps.
They showed that the property-matched columns had been drawn wrong.
They were removed from the table until they could be made to fit.
PTB-004 · hard · transfer · seq 17 · authored (UNFALSIFIABILITY-CLAIM rotation per the blueprint seq-17 contract; foils = prediction-timing re-worded, accidental-discovery overreach re-worded, completion-as-decisive (fluency-3 completion family); key invariant; elementless, no digits) · mcq4
A friend claims Mendeleev's table was never really at risk, because no discovery could have counted against it. Which possible discovery proves the friend wrong?
A gap element turning up with properties unlike those written in its prediction. KEY
Old records showing the predictions had been written long before any gap element was found.
A new element discovered by pure accident, with no help from the table or its gaps.
The last of the gaps being filled, leaving no empty cells anywhere in the table.
PTB-005 · hard · transfer · seq 18 · authored (draft-list critique rotation per the blueprint seq-18 contract: fresh letters M/G, a mass-ordered draft judged against the modern rule, second-named element keys; distractors {mass-order draft endorsement (structural foil), cannot-decide-without-properties re-worded, detached-block parking} — PTB-005 gate/fluency-recorded classes; no real elements, no digits) · mcq4
A draft list places element M before element G because M's atomic mass is smaller. G's atomic number is smaller than M's. What does the modern ordering rule say about the draft?
The draft is wrong — G belongs first, since the modern order follows increasing atomic number. KEY
The draft is right — the lighter element belongs first.
The draft cannot be judged without knowing both elements' properties.
Both orders are avoided — pairs like this are moved into the detached block printed below the table.
PTB-006 · hard · transfer · seq 19 · authored (mistake-claim rotation: vanadium 23 / niobium 41, interval 18; foils = accept-mistake (numbering-error class) / pattern-denial (fluency-1 class) / merge-same-substance) · mcq4
Vanadium is element 23 and niobium is element 41, and the two behave alike. A classmate says the match must be a mistake somewhere in the list. What does the periodic law call it?
One instance of the repeating pattern — matches one interval apart are what the law expects. KEY
Evidence of a mistake — one of the two elements must be sitting in the wrong place in the list.
Nothing at all — every element behaves in its own way, so the match carries no meaning.
Proof that vanadium and niobium are two names for one metal.
PTB-007 · hard · transfer · seq 20 · authored (REPUTATION-TIMELINE claim judgment: when did the table's evidence arrive; foils = no-match-until-after-reordering reversed-timeline / swaps-were-a-passed-test miscast wrong-reason / judgment-reserved-until-gaps-filled closed-the-table) · mcq4
A student claims Mendeleev's table earned its reputation only after the reordering by atomic number, because nothing had tested the table before then. Judge the claim against the historical record.
The claim is wrong — discoveries matching the gap predictions had tested the table, and made its name, decades before the reordering. KEY
The claim is right — no element matching a gap prediction was discovered until after the ordering had been corrected.
The claim is wrong, because the hand swaps were a test that the table had already passed under the mass ordering.
The claim is right — chemists reserved their judgment on the table until the last of its gaps had been filled.
PTB-004 · medium · application · seq 21 · authored (blueprint rows[20] gap-prediction FRQ; letter-element column fragment: light metals L/M, partner D, recipe two-to-one, melting AND vigor both fall down the column) | sol-loop-2: the steady column trend is now a STATED premise (two endpoint values alone underdetermine the in-between prediction; PTB-004 supplies no interpolation rule, so the scenario supplies the trend). · frq
In one column of a half-built table, a chemist following Mendeleev's method has left a cell empty: the next known element in the mass order failed to match that column's properties. The column reads, top to bottom: Element L, directly above the empty cell — a light metal; melts only at a high temperature; reacts briskly with element D; its compound with element D holds two atoms of L for every one atom of D. (the empty cell) Element M, directly below the empty cell — a light metal; melts at a much lower temperature than L; reacts slowly with element D; its compound with element D holds two atoms of M for every one atom of D. Down this column of the table, each of these properties changes steadily from one cell to the next.
In one column of a half-built table, a chemist following Mendeleev's method has left a cell empty: the next known element in the mass order failed to match that column's properties. The column reads, top to bottom: Element L, directly above the empty cell — a light metal; melts only at a high temperature; reacts briskly with element D; its compound with element D holds two atoms of L for every one atom of D. (the empty cell) Element M, directly below the empty cell — a light metal; melts at a much lower temperature than L; reacts slowly with element D; its compound with element D holds two atoms of M for every one atom of D. Down this column of the table, each of these properties changes steadily from one cell to the next. (a) The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now. (b) Predict each of the missing element's properties: the recipe of its compound with element D, its melting behavior, and how briskly it reacts with element D. Justify each prediction by pointing to the properties of element L and element M. (c) Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Part a. The missing element has not been discovered yet. State what Mendeleev's method allows the chemist to write in the empty cell, say what sort of values those are, and explain why that is the only sort possible for this cell right now.
Model: The method allows him to write the missing element's predicted properties, read from the elements around the gap — here, from element L above and element M below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured.
Part b. Predict each of the missing element's properties: the recipe of its compound with element D, its melting behavior, and how briskly it reacts with element D. Justify each prediction by pointing to the properties of element L and element M.
Model: Compound recipe with D: two atoms of the missing element for every one atom of D — element L and element M both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — it should melt at a lower temperature than L but a higher temperature than M, because melting drops from L down to M and the missing element sits between them. Reaction vigor with D: in between as well — calmer than L but livelier than M, continuing the same downward change; here BOTH graded properties fall down the column, and each prediction follows its own neighbors' bracket. None of these values are copied from either neighbor: L and M set the pattern, and the prediction continues it.
Part c. Years later, a new element is discovered that fills this gap. State what its measured properties would have to show for the discovery to confirm the predictions, and state what they would have to show to be evidence that the table's pattern had failed.
Model: To confirm: the discovered element's measured properties must match the written predictions — the two-atoms-to-one-atom recipe with D, melting between M's and L's, and reaction vigor with D between the two. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with D, or melting and vigor falling outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.
Full model answer. (a) The method allows him to write the missing element's predicted properties, read from the elements around the gap — here, from element L above and element M below. They are predictions, and predictions are the only possible kind: the element has never been found, so no sample of it exists, and with no sample nothing about it can be measured. (b) Compound recipe with D: two atoms of the missing element for every one atom of D — element L and element M both carry exactly that recipe, so the column's shared recipe continues through the cell between them. Melting behavior: in between its neighbors — it should melt at a lower temperature than L but a higher temperature than M, because melting drops from L down to M and the missing element sits between them. Reaction vigor with D: in between as well — calmer than L but livelier than M, continuing the same downward change; here BOTH graded properties fall down the column, and each prediction follows its own neighbors' bracket. None of these values are copied from either neighbor: L and M set the pattern, and the prediction continues it. (c) To confirm: the discovered element's measured properties must match the written predictions — the two-atoms-to-one-atom recipe with D, melting between M's and L's, and reaction vigor with D between the two. Evidence against: the same discovery with measured properties that do NOT match the predictions — a different recipe with D, or melting and vigor falling outside what the neighbors bracket. The test comes only when the element is found and measured: a match is evidence the table's pattern is real, and a mismatch would have shown the pattern failing exactly where it made its claim.

End of Topic Test: Metals, nonmetals, and metalloids & Position and electron arrangement & Chemical families (u03-t2 · 5 forms × 21 items · 105 total)

David's notes for James:
full notes file
# u03-t2 — notes/queries from David's side (U3-G2)

1. FAMILY-GATE INSTANCE ADJUDICATION: chemical-families content is nature-fixed - the member elements, the taught reaction partners (water/air), and group numbers 13-18 ARE the tested mapping, so cross-slot instance exclusivity is structurally unsatisfiable for parts of this gate. Everything text-fixable WAS content-fixed (102 patch ops: all 21 spec-text gram reuses reworded, all 25 cross-form gram reuses broken, all 5 within-form adjacent same-material pairs re-instanced). The irreducible residue is covered by 14 recorded adjudicated_instance_families in gate_config.json (slots + exact tokens + rationale each), enforced by the gate-local validate_with_adjudications.py wrapper over the untouched _shared validator (U2-G2 precedent). Retake leakage between forms is the accepted cost - flag if any family should be redistributed.
2. NOTA REPLACEMENTS (6 seed slots, opportunistic rule): your PTB-011 seeds (pool 9/10/11 -> seq 6 on forms A/B/C) and PTB-013 seeds (pool 15/16/17 -> seq 7 on forms A/B/C) each carry the spec-sanctioned literal 'None of the above.' fourth seat ('only three classes exist'). Each was replaced with a substantive misconception-keyed distractor with everything else kept byte-verbatim: seq-6 got dual-membership / split-sample / class-hedge blend seats; seq-7 got family-for-class swaps ('An alkali metal.' / 'A halogen.' / 'A transition metal.' - each positionally ruled out by the marked cell). Please confirm the replacement seats.
3. NUMERIC UNITS (seq 8 shells-from-period, seq 9 valence-from-group): your seeds carry an empty unit_label, so the exported answers complete it with count words ('shells', 'valence electrons' - U2-G1 count-word precedent). Grading is on the numeric value only (exact integers, tolerance 0); the sigFigs field is display metadata carried to satisfy the test numeric contract, not an assessed requirement (precisionAssessed:false, the U01-G2/G3 convention; per-item gradingNote states this).
4. AUTHORED FRQ (seq 21): PTB-029's prod_seeds list is EMPTY and its pool holds no productions, so the terminal FRQ is authored (U2-G2 fallback precedent): supplied group number -> (a) name the family, (b) two distinct taught-profile predictions, (c) the valence-electron account of WHY, rubric 30/40/30. Instances rotate a different family per form: A fluorine (Group 17), B calcium (Group 2), C potassium (Group 1), D neon (Group 18), E chlorine (Group 17 again - the halogen family carries two forms on different instances; recorded row-21 judgment).
5. RECORDED CONSTRUCT OVERRIDES (our authoritative QC model maintains 3 objections; course-local authority applied, David's sign-off pending): (1) A#4 is PTB-027 gateItems[0] VERBATIM - the QC model reads the Groups 3-12 location read as PTB-014's skill, but PTB-027's own article setup teaches the location and its own gate design tests it; (2)+(3) FRQ part (c) on all five forms - the QC model reads the valence-electron account as PTB-020/PTB-024 mechanism overreach, but PTB-029 rule 2 ('the family's shared valence-electron count sets the behavior') makes it the capstone's own taught chain and the blueprint FRQ contract explicitly requires it. Flag if you want part (c) narrowed instead.
6. SEQ-20 CAPSTONE INSTANCE MOVED OFF THE NOBLE GASES: all six noble gases are exercised in PTB-025/026/029 fluency (student-seen), so ANY noble-gas capstone instance would be memory-answerable, and D#21's FRQ owns neon. E#20 was re-familied neon -> osmium (transition profile); the seq-20 family rotation is now Group-2 / transition / halogen / alkali / transition (forms B and E share the transition profile on different instances - recorded).
7. SAME-FORM HALOGEN-SALT + HALOGEN-FRQ PAIRING (forms A and E): A#19 (iodide prediction) + A#21 (fluorine FRQ) comes from your own seed placement; E#19 (calcium+iodine, the within-form water-adjacency fix) + E#21 (chlorine FRQ) reproduces the same class. Part-(b) rubric credit comes from taught family-profile lines either way; recorded as accepted.
8. Blind-review figure family 'periodic-table-regions' (the seq-7 unshaded table outlines) was rendered positionally by a gate-local packet augmenter; documented as a _shared make_blind_packet.py candidate for the maintainer, not applied this wave (_shared read-only).

Form A

PTB-008 · easy · recall · seq 1 · seed:U3-G2/pool[0] (= PTB-008 gateItems[0]) - stem/options/misconception clauses/explanation VERBATIM (placement flags EMPTY; no NOTA; no material instances in student-visible text; formatting-only: <p> strip + house feedback composition). The seed explanation names mercury inside the package sentence — feedback fields sit outside the V-T7 FIELD SCOPE and the exception is not TESTED here (form B tests it); kept verbatim. · mcq4
Which set of observations fits a typical metal?
Shiny, flattens when struck, conducts electricity well. KEY
Shiny, shatters when struck, conducts electricity poorly.
Dull, shatters when struck, does not conduct electricity.
Dull, flattens when struck, does not conduct electricity.
PTB-019 · easy · recall · seq 2 · seed:U3-G2/pool[35] (PTB-019 gateItems[2], hydrogen-exclusion) — stem/options/feedback/explanations byte-VERBATIM; bare element options per R11 mandated by PTB-019 specNotes; stage-1 freshness_same_lesson flag = the membership FACT (scoped family-atom exception); stage-3 fallback per seed_placement: swap A#10 to pool 29 (element-free) or rotate this seed off form A · mcq4
Which element sits in Group 1 but is not an alkali metal?
Hydrogen KEY
Lithium
Sodium
Cesium
PTB-023 · easy · recall · seq 3 · seed:U3-G2/pool[46] (= PTB-023 gateItems[1]) - stem/options/misconception clauses/explanation VERBATIM (placement flags empty; no NOTA; no material instances in V-T7-scanned fields; formatting-only: <p> strip + house feedback composition; the seed keyExplanation's sodium-chloride mention is post-answer feedback, outside V-T7 FIELD SCOPE - see authoring notes) · mcq4
Which statement about the halogens is correct?
They react with metals, and the compounds formed are salts. KEY
They are unreactive gases used to fill balloons.
They are shiny metals that conduct electricity well.
They travel as single atoms, never joined to anything.
PTB-027 · easy · recall · seq 4 · seed:U3-G2/pool[57] (PTB-027 gateItems[0], James) — VERBATIM: stem, key, distractors, misconceptions, explanation; zero stage-1 flags; element-free; EXPECTED stage-3 V-T7 structural-number surface on 13/17/18 recorded in authoring_notes (rule-content class, fluorine precedent — adjudication candidate, gate_config ships empty) · mcq4
In which groups of the periodic table do the transition metals sit?
Groups 3 through 12 KEY
Groups 1 and 2
Groups 13 through 18
Group 17 only
PTB-009 · medium · application · seq 5 · seed:U3-G2/pool[4] (= PTB-009 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; freshness_same_lesson flag (oxygen) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates · mcq4
Oxygen spreads to fill every corner of the room you are sitting in, yet none of it is visible anywhere. Which part of the nonmetal package does that show?
Many nonmetals are gases at room temperature. KEY
Nonmetals are dull rather than shiny.
Nonmetals conduct electricity poorly.
Solid nonmetals are brittle.
PTB-011 · medium · application · seq 6 · seed:pool[9] (PTB-011 gateItems[0]; stem/key/distractors b,c/explanation VERBATIM; NOTA seat d REPLACED with the dual-membership blend per replace_distractor [ANSWERS #2] — RECORD FOR DAVID_REVIEW; explanation = seed text + one dispatch sentence) · mcq4
Tellurium is silvery-white, shatters when hammered, and conducts electricity weakly. Classify tellurium.
A metalloid. KEY
A metal.
A nonmetal.
Both a metal and a nonmetal at once.
PTB-013 · medium · application · seq 7 · seed:U3-G2/pool[15] (PTB-013 gateItems[0]) — stem, key, distractors b/c + feedback, both explanations, and figureSpec byte-VERBATIM; single edit = flagged replace_distractor: NOTA fourth seat -> 'An alkali metal.' (family-for-class swap, positionally ruled out: Group 1 is the leftmost column, the marked cell sits deep in the center block; NOT the banned 'A transition metal.', which is truthy for a center-block cell) · mcq4
A cell is marked on the table outline, deep in the middle of the center block. Classify the element that lives there.
FIGURE (periodic-table-regions · stimulus) — shadedRegions: [] · regionLabels: false · stairStep: true · markedCells: [{"label": "X", "position": "center of the middle block"}] · style: "unshaded outline, stair-step drawn, one unlabeled cell marked X"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-regions",
  "shadedRegions": [],
  "regionLabels": false,
  "stairStep": true,
  "markedCells": [
   {
    "label": "X",
    "position": "center of the middle block"
   }
  ],
  "style": "unshaded outline, stair-step drawn, one unlabeled cell marked X"
 }
}
A metal. KEY
A metalloid.
A nonmetal.
An alkali metal.
PTB-015 · medium · application · seq 8 · seed:U3-G2/pool[21] (PTB-015 gateItems[0], barium period-read) — James's stem template, exact-integer answer contract (tolerance 0), and group-read diagnostic class kept; must_freshen_instance EXECUTED per seed_placement/blueprint: barium (collides with the A#20 curated capstone stem's barium) -> magnesium, Period 6 -> Period 3, answer 6 -> 3; magnesium is Group 2 like barium so the seed's anticipated-wrong value (2, group read) carries over unchanged; the seed's 'however deep the row' clause removed as a Period-6 artifact (QB 3.9 leftover sweep; reused on form C where it is true); V-T6 contract completion: unit '' -> 'shells' (count word), sigFigs null -> 1 + integer:true + precisionAssessed:false (recorded stage-2 adjudication, flag for David/James) · numeric
Magnesium sits in Period 3 of the periodic table. How many occupied electron shells does a magnesium atom have?
Answer: 3 shells KEY
also accepted: 3 shells, 3.0
wrongValueDiagnostics
[
 {
  "value": 2,
  "misconception": "you used magnesium's group instead of its period — the row gives the shell count",
  "feedback": "This answer is wrong — 2 is magnesium's group number. The row, not the column, gives the shell count: magnesium sits in Period 3, so a magnesium atom has three occupied shells."
 },
 {
  "value": 12,
  "misconception": "you gave magnesium's atomic number — the proton count is not the shell count",
  "feedback": "This answer is wrong — 12 is magnesium's proton count, not its shell count. The period number gives the shell count: magnesium sits in Period 3, so a magnesium atom has three occupied shells."
 }
]
feedback
{
 "keyExplanation": "Magnesium is a main-group element in Period 3. The period number equals the number of occupied shells. A magnesium atom has three occupied shells.",
 "anticipatedWrong": [
  {
   "value": 2,
   "misconception": "you used magnesium's group instead of its period — the row gives the shell count",
   "feedback": "This answer is wrong — 2 is magnesium's group number. The row, not the column, gives the shell count: magnesium sits in Period 3, so a magnesium atom has three occupied shells."
  },
  {
   "value": 12,
   "misconception": "you gave magnesium's atomic number — the proton count is not the shell count",
   "feedback": "This answer is wrong — 12 is magnesium's proton count, not its shell count. The period number gives the shell count: magnesium sits in Period 3, so a magnesium atom has three occupied shells."
  }
 ]
}
PTB-016 · medium · application · seq 9 · seed:U3-G2/pool[24] (= PTB-016 gateItems[0], James — the helium exception, single-tested per specNotes) — VERBATIM except ONE recorded stem token: 'Group 18' -> 'Group Eighteen' (SEED RULING content freshening; digit 18 in a stem = unconditional V-T7 numeric FAIL vs PTB-014/016/023/025/029 spec text). Answer, check, misconception value 8, and James's explanation text carried verbatim (digits kept in feedback — unscanned). V-T6 contract completion: unit_label '' -> unit 'valence electrons' (count words, blueprint note), sigFigs null -> 1 countable display digit + integer:true + precisionAssessed:false (recorded stage-2 adjudication). KNOWN ADJUDICATED stage-3 line: helium own-lesson material reuse (helium is named by PTB-016's own rule line and IS the pinned exception instance — see authoring_notes; scoped relief documented, not applied). · numeric
Helium sits in Group Eighteen of the periodic table. How many valence electrons does a helium atom have?
Answer: 2 valence electrons KEY
also accepted: 2 valence electrons, two, 2.0
wrongValueDiagnostics
[
 {
  "value": 8,
  "misconception": "you applied the subtract-10 rule — helium is the exception, with only two electrons in total",
  "feedback": "This answer is wrong — 8 comes from applying the subtract-10 rule to Group 18. Helium is the one exception in Group 18: a helium atom has only two electrons in total, so it has two valence electrons, not eight."
 }
]
feedback
{
 "keyExplanation": "Helium is the one exception in Group 18. A helium atom has only two electrons in total. So helium has two valence electrons, not eight.",
 "anticipatedWrong": [
  {
   "value": 8,
   "misconception": "you applied the subtract-10 rule — helium is the exception, with only two electrons in total",
   "feedback": "This answer is wrong — 8 comes from applying the subtract-10 rule to Group 18. Helium is the one exception in Group 18: a helium atom has only two electrons in total, so it has two valence electrons, not eight."
  }
 ]
}
PTB-017 · medium · application · seq 10 · seed:U3-G2/pool[27] (= PTB-017 gateItems[0], James) — stem/key/distractor texts/misconception clauses/explanation VERBATIM; formatting-only: <p> strip + house feedback composition; placement flags freshness_scope_article (cesium, lithium — scope-article WARN class) CARRIED, no fix applied per seed doctrine, stage-3 validator arbitrates; recorded fallback (seed_placement A#2 note): if V-T7 trips on the form-A Li/Cs pileup (A#2's bare option labels vs this stem), swap A#10 to pool 29 (element-free; currently C#10, so C#10 would be re-authored) or rotate the A#2 seed off form A · mcq4
A student says lithium and cesium behave alike because their atoms are nearly the same size. Correct the reason.
The sizes differ — the elements behave alike because their atoms have the same number of valence electrons. KEY
The student is right — atoms of the same group are the same size.
The elements behave alike because their atoms have the same number of occupied shells.
The elements do not behave alike, because their masses are so different.
PTB-018 · medium · application · seq 11 · seed:U3-G2/pool[31] (= PTB-018 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; element-free; zero placement flags; 'Nothing is wrong' seat = claim-evaluation option, substantive, not NOTA (blind watch carried from seed_placement) · mcq4
A student claims: 'Properties repeat across the periodic table because atoms get heavier at a steady rate.' What is wrong with the claim?
Steady mass growth cannot cause repeats — the pattern comes from the valence count starting over each period. KEY
Nothing is wrong — atoms getting steadily heavier is exactly what produces the repeating pattern.
The claim starts from a false premise — properties do not actually repeat across the table.
Atoms actually get lighter along the list.
PTB-020 · medium · application · seq 12 · seed:U3-G2/pool[37] (= PTB-020 gateItems[1]) — stem/key/distractors/misconception clauses/explanation VERBATIM (placement flags EMPTY; element-free; no NOTA; formatting-only: <p> strip + house feedback composition, first clause closed as a sentence — U01-G2/U2-G2 canon). The key is the lesson's fluency-0 key verbatim = MECH-METAL-LOSS-HS voiced with the easy-removal clause, per specNotes ('carried verbatim as rule line 1 and echoed in keys') — every key gram sits in the runtime A3 whitelist. · mcq4
A student writes: 'Alkali metals are reactive because their atoms want a full outer shell.' The course's account is more specific. Which statement is it?
A metal atom reacts by giving away its outer electrons, and an alkali metal atom's single valence electron is easy to remove. KEY
An alkali metal atom grabs seven more electrons to complete its outer shell.
An alkali metal atom's inner shells push the outer electron out on their own.
Alkali metal atoms react because they contain more electrons in total than the atoms of any other element.
PTB-021 · medium · application · seq 13 · seed:U3-G2/pool[40] (= PTB-021 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; zero placement flags; element-free. STAGE-3 WATCH: key is the form's longest option (78 vs 58/48/42) — if V-T4 fails, rebalance the distractors, never the validator · mcq4
Which observation would tell you a water-reactive metal sample is an alkaline earth metal rather than an alkali metal?
It reacts less violently than an alkali metal and is harder to cut. KEY
It reacts the instant it hits the water and can be cut like cheese.
It sits in water for days without reacting at all.
It is a colorless gas at room temperature.
PTB-024 · medium · application · seq 14 · seed:U3-G2/pool[49] (= PTB-024 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; zero placement flags; element-free mirror comparison (placed on A to dodge A#19's iodine per seed_placement); stage-3 watch: key is the form's longest option (seed kept verbatim, seed doctrine) · mcq4
A student says: 'Halogens and alkali metals are both very reactive, so their atoms must be doing the same thing.' What is the correct comparison?
Both react readily, but the metal atoms give an electron away while the halogen atoms pull one in. KEY
The student is right — both kinds of atoms give away one valence electron.
The student is right — both kinds of atoms pull in one extra electron.
Neither family's atoms move electrons at all; the reactivity is about their molecules.
PTB-025 · medium · application · seq 15 · seed:U3-G2/pool[52] (= PTB-025 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; freshness_scope_article flag (nitrogen, oxygen) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates · mcq4
Deep-sea divers breathe a mix in which much of the nitrogen is replaced by a Group 18 gas. Why is a Group 18 gas a chemically safe replacement?
Noble gases almost never react, so the gas passes in and out of the body without chemically changing anything. KEY
Noble gases react inside the tank to make extra breathable gas for the diver.
Noble gases are heavier than air, so they sink safely to the bottom of the diver's tank and stay there.
Noble gases burn away any dangerous gases in the mix.
PTB-026 · medium · application · seq 16 · seed:U3-G2/pool[54] (= PTB-026 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; freshness_scope_article flag (krypton) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates · mcq4
Krypton is sealed between the panes of some high-end windows, against glass, metal spacers, and years of sunlight. Why does the krypton survive chemically unchanged?
Its atoms' full outer shells give them little tendency to gain, lose, or share electrons. KEY
Sunlight empties krypton's outer shell, and empty shells cannot react.
Krypton reacts with the glass first, and that reaction protects the rest of the gas.
Krypton's atoms share their electrons with the metal spacers, and the sharing keeps everything calm.
PTB-014 · hard · transfer · seq 17 · seed:U3-G2/pool[18] (= PTB-014 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; freshness_same_lesson flag (gallium, zinc) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates; the spec's dedicated 12/13 hard case (four assignment permutations, MPM-020 precedent) · mcq4
Zinc occupies Group 12, and gallium occupies Group 13. Classify the pair.
Zinc: a transition metal. Gallium: a main-group element. KEY
Both are transition metals.
Both are main-group elements.
Zinc: a main-group element. Gallium: a transition metal.
PTB-022 · hard · transfer · seq 18 · seed:U3-G2/pool[43] (= PTB-022 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_same_lesson flag (rubidium/strontium, the lesson's fluency-3 pair) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates; option b 'Nothing is wrong' = substantive claim-evaluation seat, blind-review watch; explanation's 'the faster reactor' = chemistry sense, covered by the blueprint's recorded wave-3 scan adjudication. STAGE-3 WATCH: key is the form's unique longest option (103 vs 101/64/59) — if V-T4 fails, rebalance the distractors, never the validator · mcq4
A student claims: 'Strontium should react faster than rubidium, because with two valence electrons it has twice as much to offer the water.' What is wrong with the claim?
Removing two valence electrons takes more energy than removing one, so strontium is the slower reactor. KEY
Nothing is wrong — strontium's extra valence electron really does make it react faster than rubidium.
The claim fails because strontium has only one valence electron.
The claim fails because rubidium never reacts when it is put in water.
PTB-028 · hard · transfer · seq 19 · seed:U3-G2/pool[62] (= PTB-028 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; flags freshness_same_lesson (iodine, sodium — sodium is the stem's own supplied datum per specNotes) + freshness_scope_article (francium) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates; 'No prediction is possible…' seat = deliberate substantive escape-hatch (specNotes; U2-G3 class), NOT V-T5 NOTA — blind-review watch note recorded · mcq4
Sodium and iodine react, and the product is sodium iodide. Francium sits at the bottom of sodium's group, and no chemistry class has a francium sample. Which prediction does the family pattern justify?
Francium would react with iodine, giving francium iodide. KEY
Francium would react with iodine, giving sodium iodide.
No prediction is possible for an element nobody has handled.
Francium would react with sodium instead of with iodine.
PTB-029 · hard · transfer · seq 20 · seed:U3-G2/pool[63] (= PTB-029 gateItems[0] = demo_curated[0], James CURATED — both refs cited per seed_placement) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_same_lesson (barium) + freshness_scope_article (calcium, radium) flags carried, no fix applied (U2-G1 rule: the curated capstone keeps its instances — the colliding A#8 barium freshens instead, blueprint adjudication); radium framing = family water-reactivity only, no radiation language (wave-3 scan adjudication); 'Nothing —' seat = claim-evaluation option, substantive, NOT V-T5 NOTA (blind watch). STAGE-3 WATCH: key is the form's unique longest option (105 vs 89/83/95) — if V-T4 fails, rebalance the distractors, never the validator · mcq4
Radium sits in Group 2, below barium and calcium. A museum label calls it 'the one Group 2 metal that leaves water completely alone'. Judged by its family, what is wrong with the label?
Group 2's profile covers every member — radium, like barium and calcium, should react with water and air. KEY
Nothing — an element as rare as radium cannot be expected to follow its family's profile.
Radium is a noble gas, so the label is wrong to call it a metal in the first place.
The label exempts the wrong metal — it is barium that leaves water untouched.
PTB-029 · medium · application · seq 21 · authored (unseeded by design — gate-wide zero FRQ/production seeds: prod_seeds EMPTY and the 66-item pool is 62 mcq + 4 numeric; blueprint rows[20] seq-21 AUTHORED-FRQ directive on the capstone lesson, U2-G2 fallback precedent; instance = fluorine with Group 17 supplied on a storeroom supplies-log surface; part (c) account = the PTB-024 halogen pull, integrated per the capstone chain of PTB-029 rule 2) · frq
A storeroom's incoming-supplies log lists a new sealed sample tube. The entry reads 'fluorine', and the only other detail recorded is the element's group: Group 17.
A storeroom's incoming-supplies log lists a new sealed sample tube. The entry reads 'fluorine', and the only other detail recorded is the element's group: Group 17. (a) Using only the group number in the log entry, name the chemical family fluorine belongs to, and state how you can tell from that one detail. (b) Predict two ways fluorine should behave. Each prediction must be a behavior fluorine's whole family shares, stated as a prediction about fluorine itself. (c) Explain why fluorine's family is so reactive, in terms of the atoms' valence electrons.
Part a. Using only the group number in the log entry, name the chemical family fluorine belongs to, and state how you can tell from that one detail.
Model: Group 17 is the halogen group, so fluorine is a halogen. The group number alone settles it: the group names the chemical family, and the log already supplies the group — no periodic-table lookup and no other fact about fluorine is needed. Answer: Fluorine is a halogen — Group 17 names the halogen family, so the group number in the log is enough by itself.
Part b. Predict two ways fluorine should behave. Each prediction must be a behavior fluorine's whole family shares, stated as a prediction about fluorine itself.
Model: The taught halogen profile: a very reactive nonmetal; travels as two-atom molecules — each moving particle a pair of identical atoms; reacts with metals, and the compound formed with a metal is a salt. Any two, applied to fluorine — for example: fluorine should be a very reactive nonmetal, and fluorine should react with metals, forming salts. A third acceptable prediction: fluorine should travel as two-atom molecules rather than as single atoms. Not acceptable: a ranking against other halogens — which halogen reacts fastest is not part of the taught profile. Answer: Any two of: a very reactive nonmetal; travels as two-atom molecules; reacts with metals to form salts — each stated as a prediction about fluorine.
Part c. Explain why fluorine's family is so reactive, in terms of the atoms' valence electrons.
Model: A halogen atom has seven valence electrons — one electron short of a full outer shell. Being one electron short, the atom pulls in that missing electron very readily. That ready pull is what makes the whole family so reactive — fluorine's predicted eagerness toward metals is its atoms pulling in the one electron they lack. Answer: A halogen atom has seven valence electrons — one short of a full outer shell — so it pulls in the missing electron very readily; that ready pull is why the family is so reactive.
Full model answer. (a) Group 17 is the halogen group, so fluorine is a halogen. The group number alone settles it: the group names the chemical family, and the log already supplies the group — no periodic-table lookup and no other fact about fluorine is needed. Answer: Fluorine is a halogen — Group 17 names the halogen family, so the group number in the log is enough by itself. (b) The taught halogen profile: a very reactive nonmetal; travels as two-atom molecules — each moving particle a pair of identical atoms; reacts with metals, and the compound formed with a metal is a salt. Any two, applied to fluorine — for example: fluorine should be a very reactive nonmetal, and fluorine should react with metals, forming salts. A third acceptable prediction: fluorine should travel as two-atom molecules rather than as single atoms. Not acceptable: a ranking against other halogens — which halogen reacts fastest is not part of the taught profile. Answer: Any two of: a very reactive nonmetal; travels as two-atom molecules; reacts with metals to form salts — each stated as a prediction about fluorine. (c) A halogen atom has seven valence electrons — one electron short of a full outer shell. Being one electron short, the atom pulls in that missing electron very readily. That ready pull is what makes the whole family so reactive — fluorine's predicted eagerness toward metals is its atoms pulling in the one electron they lack. Answer: A halogen atom has seven valence electrons — one short of a full outer shell — so it pulls in the missing electron very readily; that ready pull is why the family is so reactive.

Form B

PTB-008 · easy · recall · seq 1 · seed:U3-G2/pool[1] (= PTB-008 gateItems[1]) - the mercury-exception state read, VERBATIM (placement flag freshness_same_lesson anticipated this; formatting-only: <p> strip + house feedback composition). DETERMINISTIC STAGE-3 V-T7 FOOTPRINT, documented in authoring_notes[2]: exactly ONE fail — own-lesson taught-material 'mercury' (the key's rule-line grams are cleared by the UNFILTERED rule-gram whitelist class, verbatim-rule doctrine; verified with the validator's own machinery). Rule-content by design; resolution = recorded gate_config adjudication (U2-G2 wrapper own_mat class, no wrapper extension needed), NOT a seed reword and NOT a _shared change. · mcq4
At room temperature, what does the metal class look like state-wise?
All solids except mercury, which is a liquid. KEY
All solids, without exception.
Mostly liquids, with a few solids.
A mix of solids, liquids, and gases.
PTB-019 · easy · recall · seq 2 · authored (softness + fresh-cut shine facet, rule line 1; element-free; misconception classes = hardened-them / soft-means-crumbly / dull-throughout, fresh wording; melting class dropped — cesium hand-warmth hazard) · mcq4
An alkali-metal sample has just been cut open. Which description fits?
The knife cut it easily, and the fresh surface was shiny. KEY
It was too hard to cut — even a saw left only a scratch.
It crumbled into dull powder as soon as the blade touched it.
The cut surface came out dull gray and never turned shiny at all.
PTB-023 · easy · recall · seq 3 · authored (two-atom-molecule case on a pure-sample particle-read surface; element-free, digit-free; key anchored on the lesson's canonical pair wording — fluency-3 key + rule line, both runtime A3 whitelist sources; taught misconception classes from fluency-3, metal-partner distractor made element-free) · mcq4
A sealed flask holds a sample of one pure halogen. How do its atoms move around inside the flask?
In pairs — each molecule is two identical atoms of the halogen. KEY
One at a time — every moving particle is a single, unattached atom.
In large clusters of many atoms that grow and shrink as they move.
In pairs — but each pair is one halogen atom holding one metal atom.
PTB-027 · easy · recall · seq 4 · authored (D8 recognition-light package read; 'typical' hedge in the stem; key = rule-line-1 profile in fresh singular phrasing; distractors = the three taught wrong-family profiles, fluency-0's misconception classes reworded; element-free, digit-free) · mcq4
Which description fits a typical transition metal?
It is hard and dense, and it conducts heat and electricity well. KEY
It is soft enough to cut with a knife, and it is violently reactive.
It is dull and brittle, and it conducts heat and electricity poorly.
It is a colorless gas, and it almost never takes part in reactions.
PTB-009 · medium · application · seq 5 · seed:U3-G2/pool[5] (= PTB-009 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA, zero placement flags; element-free unnamed rod · mcq4
A rod made from a solid nonmetal element is held at one end while the far end is heated in a flame. What do you expect at the held end, and why?
It stays cool for a long time, because nonmetals conduct heat poorly. KEY
It quickly becomes too hot to hold, because heat races through solids.
It flattens where it is held, because heated solids soften.
It begins to conduct electricity, because heat turns into current.
PTB-011 · medium · application · seq 6 · seed:pool[10] (PTB-011 gateItems[1]; stem/key/distractors b,c/explanation VERBATIM; NOTA seat d REPLACED with the split-sample blend per replace_distractor [ANSWERS #2] — RECORD FOR DAVID_REVIEW; explanation = seed text + one dispatch sentence) · mcq4
An element's surface is dull gray, but it flattens under a hammer and conducts electricity well. Classify it.
A metal. KEY
A nonmetal.
A metalloid.
Half metal, half nonmetal.
PTB-013 · medium · application · seq 7 · seed:U3-G2/pool[16] (PTB-013 gateItems[1]) — stem, key, distractors b/c + feedback, and both explanations byte-VERBATIM; edits = flagged replace_distractor: NOTA fourth seat -> 'A halogen.' (family slid one column: Group 17 is one column in from the edge, the marked cell is the far right column itself; krypton's taught noble-gas membership kills it too); PLUS figure augmentation only: markedCell gains its drawn position 'far right column, partway down' (blind self-containment; matches the stem, krypton = Period 4). Stage-1 freshness_same_lesson flag (krypton) carried, validator arbitrates; B#16 (pool 55) is element-free so B's krypton stands alone · mcq4
Krypton's cell carries the mark on the outline, in the far right column. Classify krypton from its position.
FIGURE (periodic-table-regions · stimulus) — shadedRegions: [] · regionLabels: false · stairStep: true · markedCell: {"symbol": "Kr", "name": "krypton", "position": "far right column, partway down"} · style: "unshaded outline, stair-step drawn, one cell marked with its symbol"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-regions",
  "shadedRegions": [],
  "regionLabels": false,
  "stairStep": true,
  "markedCell": {
   "symbol": "Kr",
   "name": "krypton",
   "position": "far right column, partway down"
  },
  "style": "unshaded outline, stair-step drawn, one cell marked with its symbol"
 }
}
A nonmetal. KEY
A metalloid.
A metal.
A halogen.
PTB-015 · medium · application · seq 8 · authored (James's PTB-015 period-read template kept verbatim-parallel; fresh instance: germanium, Period 4 -> 4; zero covered-corpus occurrences — lives only in subsumed PTB-010's article, the blueprint's documented watch class; element-disjoint from B#9's tin per the blueprint's seq-8/9 mandate; minus-ten diagnostic UNDEFINED here — 14 - 10 equals the key — so the taught atomic-number class is the second diagnostic, recorded adjudication) · numeric
Germanium sits in Period 4 of the periodic table. How many occupied electron shells does a germanium atom have?
Answer: 4 shells KEY
also accepted: 4 shells, 4.0
wrongValueDiagnostics
[
 {
  "value": 14,
  "misconception": "you used germanium's group instead of its period — the row gives the shell count",
  "feedback": "This answer is wrong — 14 is germanium's group number. The row, not the column, gives the shell count: germanium sits in Period 4, so a germanium atom has four occupied shells."
 },
 {
  "value": 32,
  "misconception": "you gave germanium's atomic number — the proton count is not the shell count",
  "feedback": "This answer is wrong — 32 is germanium's proton count, not its shell count. The period number gives the shell count: germanium sits in Period 4, so a germanium atom has four occupied shells."
 }
]
feedback
{
 "keyExplanation": "Germanium is a main-group element in Period 4. The period number equals the number of occupied shells. A germanium atom has four occupied shells.",
 "anticipatedWrong": [
  {
   "value": 14,
   "misconception": "you used germanium's group instead of its period — the row gives the shell count",
   "feedback": "This answer is wrong — 14 is germanium's group number. The row, not the column, gives the shell count: germanium sits in Period 4, so a germanium atom has four occupied shells."
  },
  {
   "value": 32,
   "misconception": "you gave germanium's atomic number — the proton count is not the shell count",
   "feedback": "This answer is wrong — 32 is germanium's proton count, not its shell count. The period number gives the shell count: germanium sits in Period 4, so a germanium atom has four occupied shells."
  }
 ]
}
PTB-016 · medium · application · seq 9 · seed:U3-G2/pool[25] (= PTB-016 gateItems[1], James — subtract-10 with the deep-period distractor) — VERBATIM except TWO recorded stem freshenings (SEED RULING): (1) 'Group 14' -> 'Group Fourteen' (digit 14 in a stem = V-T7 numeric FAIL vs PTB-014 spec text; the word 'fourteen' appears in no scope blob); (2) 'Tin sits in' -> 'Tin is found in' (the 4-gram 'tin sits in group' is PTB-014's own worked-example text — 'Q: Tin sits in Group 14. Is tin a main-group element or a transition metal?' — a machine-verified V-T7 spec-text reuse FAIL; the verb swap breaks the gram while keeping James's item intact). Answer, check, both misconception values (14, 5), and James's explanation text carried verbatim. V-T6 contract completion as on form A. Carried WARN (seed doctrine, stage-1 flag): tin is a MATERIALS word taught in PTB-014's blob -> other-lesson WARN (tin is also PTB-014's student-seen WE instance — stage 1 placed it knowing the flag). LEDGER: tin is MECHANICALLY blocked for the adjacent row08 form-B instance and for every other form-B row. · numeric
Tin is found in Group Fourteen of the periodic table, in Period 5. How many valence electrons does a tin atom have?
Answer: 4 valence electrons KEY
also accepted: 4 valence electrons, four, 4.0
wrongValueDiagnostics
[
 {
  "value": 14,
  "misconception": "you gave the group number itself — for Groups 13 through 18, subtract 10",
  "feedback": "This answer is wrong — 14 is the group number itself. For Groups 13 through 18, the group number minus 10 gives the count: 14 − 10 = 4, so a tin atom has four valence electrons."
 },
 {
  "value": 5,
  "misconception": "you used tin's period instead of its group — the column gives the valence count",
  "feedback": "This answer is wrong — 5 is tin's period. The column, not the row, gives the valence count: tin sits in Group 14, and 14 − 10 = 4, so a tin atom has four valence electrons. The deep period changes nothing."
 }
]
feedback
{
 "keyExplanation": "Tin is a main-group element in Group 14. Groups 13 through 18 give the group number minus 10: 14 − 10 = 4. The deep period changes nothing — a tin atom has four valence electrons.",
 "anticipatedWrong": [
  {
   "value": 14,
   "misconception": "you gave the group number itself — for Groups 13 through 18, subtract 10",
   "feedback": "This answer is wrong — 14 is the group number itself. For Groups 13 through 18, the group number minus 10 gives the count: 14 − 10 = 4, so a tin atom has four valence electrons."
  },
  {
   "value": 5,
   "misconception": "you used tin's period instead of its group — the column gives the valence count",
   "feedback": "This answer is wrong — 5 is tin's period. The column, not the row, gives the valence count: tin sits in Group 14, and 14 − 10 = 4, so a tin atom has four valence electrons. The deep period changes nothing."
  }
 ]
}
PTB-017 · medium · application · seq 10 · seed:U3-G2/pool[28] (= PTB-017 gateItems[1], James) — VERBATIM on the same terms; placement flags freshness_scope_article (hydrogen, oxygen, sulfur) CARRIED, validator arbitrates; blueprint parked pool 30 on form C so this form's O/S stands clear of seq 11 — SIBLING NOTE: row 11's authored form B must keep dodging oxygen/sulfur/selenium at seq 11 (blueprint adjacency rule) · mcq4
Oxygen and sulfur react with hydrogen in similar ways. Why?
Both are in Group 16, so their atoms have the same number of valence electrons. KEY
Both have atoms with the same total number of electrons.
Both sit in the same horizontal row of the table.
Both are gases at room temperature.
PTB-018 · medium · application · seq 11 · authored (counterfactual per the facet rotation: remove the per-period restart and predict the consequence for the repeating pattern — single-step application of rule lines 3-6, the seed-A 'only-grows-cannot-repeat' logic run forward; element-free; misconception classes = equal-mass-steps / shell-reset / behavior-link-break, fresh wording) · mcq4
A student tries a thought experiment: suppose that, all the way along the element list, the valence-electron count never started over — it simply kept climbing from the first element to the last. If atoms really worked that way, what would happen to the repeating pattern of properties?
Similar properties would stop returning at regular intervals. KEY
The repeats would go on unchanged, because they come from atomic mass growing in equal steps from each element to the next.
The repeats would go on unchanged, because the shell count would still drop back to one in each new period.
Atoms' chemical behavior would no longer have anything to do with their valence electrons.
PTB-020 · medium · application · seq 12 · seed:U3-G2/pool[36] (= PTB-020 gateItems[0]) — VERBATIM (formatting-only: <p> strip + house feedback composition). Placement flags CARRIED: freshness_same_lesson(sodium — note the stage-3 machinery puts sodium in OTHER scope lessons' spec_mats, PTB-017/018/019/021/023/026/028, so it lands as the elsewhere-in-scope WARN class) + freshness_scope_article(iron — PTB-008/013/014/027, WARN class). DETERMINISTIC STAGE-3 V-T7 FOOTPRINT measured with the validator's own machinery (rows/_check_row12.py, pinned): own-lesson taught-material 'air' (spec_mats[PTB-020] = {air, water} — air/water are the lesson's OWN taught reaction media: setup 'fresh surfaces dull within minutes in open air, and water sets off violent reactions'); cross-form substance 'sodium' vs A#19 (pool 62, sodium = that stem's own supplied datum) and 'iron' vs C#14 (pool 50); within-form ADJACENT 'air' vs B#13 (pool 39, 'Barium is kept away from air...'). ALL of it is seed-verbatim rule-content (the sodium-vs-iron transfer IS the lesson's spec-designed check; air is the taught medium) — resolution = recorded gate_config adjudicated_instance_families enforced by a U2-G2-class gate-local wrapper at stage-3 assembly (validate_with_adjudications.py precedent: own_mat + xf_sub excuse kinds cover these lines; the adjacency line needs the U2-G2 wrapper's family coverage extended to the within-form-adjacency kind — DOCUMENTED, decided at assembly, never by rewording James's seeds and never by weakening _shared). · mcq4
Sodium is stored under oil; iron is left on open shelves. Which atomic-level difference best accounts for sodium needing the protection?
A sodium atom's single valence electron is far easier to remove, so sodium atoms react with air much more easily. KEY
Sodium atoms are heavier than iron atoms, and heavy atoms react faster.
Sodium atoms pull in extra electrons from the air far more strongly than iron atoms ever do.
Iron atoms have no valence electrons to give away.
PTB-021 · medium · application · seq 13 · seed:U3-G2/pool[39] (= PTB-021 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_same_lesson (barium, family-atom scoped exception per PTB-021 specNotes) + freshness_scope_article (cesium) flags carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates; feedback c's 'the more vigorous reactor' = chemistry sense, covered by the blueprint's recorded wave-3 scan adjudication || QC-PATCH stage-3 wave-1: de-aired + de-dusted (B#12/B#13 within-form adjacency, QB sec.5; the seed's slower-hazard comparison and Group 2 profile survive) · mcq4
Barium is stored in a tightly sealed container in the stockroom, yet its label warns of a slower hazard than the cesium jar's. Which statement fits both facts?
Barium reacts just as cesium does, only less vigorously. KEY
Barium does not react at all; the sealed container just keeps the sample clean.
Barium reacts more violently than cesium, so its jar needs the stronger warning.
Barium only begins reacting when it is heated strongly.
PTB-024 · medium · application · seq 14 · seed:U3-G2/pool[48] (= PTB-024 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; freshness_same_lesson flag (iodine — the lesson's designed check instance per specNotes) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates · mcq4
Iodine is a reactive nonmetal. Which statement gives the atomic-level reason?
Each atom strongly pulls in the single electron it needs to fill its outer shell. KEY
Each atom easily gives away its seven valence electrons.
Each atom's outer shell is already full, so extra electrons bounce off and cause reactions.
Iodine atoms are heavy, and heavy atoms always react quickly.
PTB-025 · medium · application · seq 15 · seed:U3-G2/pool[53] (= PTB-025 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_same_lesson flag (chlorine — the specNotes' designed contrast check) carried, no fix applied per seed doctrine; 'Nothing rules it out' seat = claim-evaluation option, substantive, NOT V-T5 NOTA (blind-review watch); kept off form C per the blueprint (C#14 chlorine adjacency) || QC-PATCH stage-3 wave-1: key de-numbered (17/18 -> family names; seed freshening, SEED RULING — kills spec_num + xf_num lines with no content loss) · mcq4
An element is a gas at room temperature and takes part in almost no reactions. A classmate says it could be chlorine. What rules chlorine out?
Chlorine is very reactive — an almost-unreactive gas cannot be chlorine. KEY
Nothing rules it out — chlorine is also an almost unreactive gas.
Chlorine is a metal, so it cannot be a gas.
The gas's temperature — noble gases stay cooler than other gases.
PTB-026 · medium · application · seq 16 · seed:U3-G2/pool[55] (= PTB-026 gateItems[1], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA, zero placement flags; element-free three-atom contrast. STAGE-3 WATCH: seed key is the form's longest option (89 vs 47/49/67) — if V-T4 fails, re-word DISTRACTORS, log as seed deviation · mcq4
Three atoms sit side by side: one gives an electron away easily, one pulls an electron in strongly, one does neither. What distinguishes the third atom's outer shell?
It is full — a stable arrangement with little tendency to gain, lose, or share electrons. KEY
It is empty, so there is nothing to react with.
It holds exactly one electron, held very tightly.
It is one electron short, but the atom is too small to pull one in.
PTB-014 · hard · transfer · seq 17 · authored (the 2/3 boundary break per the blueprint seq-17 contract — the other dedicated hard case per extraNotes; ELEMENT-FREE by recorded instance policy: 'The group number alone decides' is the lesson's own rule register, so unnamed next-door elements carry the full task with zero instance risk on a fully-mixed form; four assignment permutations mirror the seed's proven structure at the opposite boundary) · mcq4
Two elements sit in next-door columns of the periodic table: one in Group 2 and its neighbor in Group 3. Classify the pair.
The Group 2 element is a main-group element; the Group 3 element is a transition metal. KEY
Both are main-group elements.
Both are transition metals.
The Group 2 element is a transition metal, and the Group 3 element is a main-group element.
PTB-022 · hard · transfer · seq 18 · authored (forward prediction for an unnamed same-period pair from supplied outer-electron counts — the student supplies both the energy comparison and the energy-pace link; element-free per the row INSTANCE POLICY: all four extraNotes-licensed named pairs are burned by the article WE (K/Ca), the pool-42 spare + B#12 (Na/Mg), and this row's own seeds (Rb/Sr on A, Cs/Ba on C)) · mcq4
Two silvery metals, M and Q, are immediate neighbors in one period of the periodic table. An atom of metal M carries a single outer electron; an atom of metal Q carries two. Fresh pieces of each metal are dropped into separate dishes of water, and both react. Which prediction about the two reactions follows?
Metal M reacts more vigorously — its single outer electron costs less energy to remove than metal Q's two, so its hand-over is the faster one. KEY
Metal Q reacts more vigorously — an atom with two electrons to give feeds the water double the electron supply that a single-electron atom can offer.
Metal Q reacts more vigorously — removing two electrons takes more energy, and the more energy a removal takes, the livelier the reaction it sets off.
The two metals react at exactly the same pace — both are metals, and atoms of both kinds start the reaction the same way, by giving electrons away.
PTB-028 · hard · transfer · seq 19 · authored (blueprint seq-19 contract: fresh unhandled-element prediction — radium from strontium's known bromine reaction, Group 2 metal swap downward; fresh pairings Sr+Br and Ra+Br, both chemically real; radium framing = rarity/family chemistry only per the wave-3 adjudicated class; escape-hatch seat d = substantive, blind-review watch) · mcq4
Strontium and bromine react to form strontium bromide. Radium sits at the bottom of strontium's group, and no school stockroom holds a radium sample. Which prediction does the family pattern justify?
Radium would react with bromine to form radium bromide. KEY
Radium would react with bromine to form strontium bromide.
Radium would react with bromine to form radium bromine, a mixture of the two elements.
No prediction is justified for a metal that no school stockroom has ever held.
PTB-029 · hard · transfer · seq 20 · seed:U3-G2/pool[65] (= PTB-029 gateItems[2] = demo_curated[2], James CURATED) — VERBATIM: stem, key, all three distractors, feedback, and explanations; zero placement flags; no NOTA/AOTA; the spec's one transition-block prediction (Group 9, PTB-027 recognition depth). STAGE-3 WATCH: key is the form's unique longest option (74 vs 46/40/55) — if V-T4 fails, rebalance the distractors, never the validator · mcq4
Iridium sits in Group 9. Predict the kind of element it is.
A hard, dense metal that conducts well, likely forming colorful compounds. KEY
A soft metal that erupts the moment it touches water.
A brittle nonmetal that conducts poorly.
A colorless gas that takes part in almost no reactions.
PTB-029 · medium · application · seq 21 · authored (blueprint rows[20] seq-21 AUTHORED-FRQ directive; instance = calcium with Group 2 supplied on a prep-room jar-label surface; part (c) account = the PTB-022 two-electron hand-over in the blueprint's own register — 'takes more energy', never 'ionization energy') · frq
A student is handed a sealed jar from the prep-room shelf. Its label carries the element name — calcium — and one further detail: Group 2.
A student is handed a sealed jar from the prep-room shelf. Its label carries the element name — calcium — and one further detail: Group 2. (a) Using only the group number on the jar's label, name the chemical family calcium belongs to, and state how you can tell from that one detail. (b) Predict two ways calcium should behave. Each prediction must be a behavior calcium's whole family shares, stated as a prediction about calcium itself. (c) Explain why calcium's family reacts less vigorously than the Group 1 metals, in terms of the atoms' valence electrons.
Part a. Using only the group number on the jar's label, name the chemical family calcium belongs to, and state how you can tell from that one detail.
Model: Group 2 names the alkaline earth metals. So calcium is an alkaline earth metal — the group number on the label gives the family by itself, with no periodic-table lookup and no other fact about calcium needed. Answer: Calcium is an alkaline earth metal — Group 2 names the alkaline-earth family, so the label's group number is enough by itself.
Part b. Predict two ways calcium should behave. Each prediction must be a behavior calcium's whole family shares, stated as a prediction about calcium itself.
Model: The taught alkaline-earth profile: harder metals than the alkali metals; they react with water and with air, but less vigorously than the alkali metals do. Both, applied to calcium: (1) calcium should be a metal that is harder than an alkali metal; (2) calcium should react with water and with air, but less vigorously than an alkali metal would. The comparison to the neighboring FAMILY is part of the taught profile; a speed ranking against another Group 2 member is not. Answer: Calcium should be a harder metal than the alkali metals, and it should react with water and with air — but less vigorously than an alkali metal would.
Part c. Explain why calcium's family reacts less vigorously than the Group 1 metals, in terms of the atoms' valence electrons.
Model: A metal atom reacts by giving away its outer electrons. A Group 2 atom has two valence electrons and must give away both — and removing two valence electrons takes more energy than removing one. So calcium's family still reacts — the electrons are given away — but the harder two-electron hand-over makes the reactions run less vigorously than the alkali metals' one-electron reactions. Answer: A Group 2 atom has two valence electrons and reacts by giving both away; the two-electron hand-over takes more energy than a one-electron hand-over, so the family reacts, but less vigorously than the alkali metals.
Full model answer. (a) Group 2 names the alkaline earth metals. So calcium is an alkaline earth metal — the group number on the label gives the family by itself, with no periodic-table lookup and no other fact about calcium needed. Answer: Calcium is an alkaline earth metal — Group 2 names the alkaline-earth family, so the label's group number is enough by itself. (b) The taught alkaline-earth profile: harder metals than the alkali metals; they react with water and with air, but less vigorously than the alkali metals do. Both, applied to calcium: (1) calcium should be a metal that is harder than an alkali metal; (2) calcium should react with water and with air, but less vigorously than an alkali metal would. The comparison to the neighboring FAMILY is part of the taught profile; a speed ranking against another Group 2 member is not. Answer: Calcium should be a harder metal than the alkali metals, and it should react with water and with air — but less vigorously than an alkali metal would. (c) A metal atom reacts by giving away its outer electrons. A Group 2 atom has two valence electrons and must give away both — and removing two valence electrons takes more energy than removing one. So calcium's family still reacts — the electrons are given away — but the harder two-electron hand-over makes the reactions run less vigorously than the alkali metals' one-electron reactions. Answer: A Group 2 atom has two valence electrons and reacts by giving both away; the two-electron hand-over takes more energy than a one-electron hand-over, so the family reacts, but less vigorously than the alkali metals.

Form C

PTB-008 · easy · recall · seq 1 · authored (package case rotated onto a wrong-line poster surface; the three true lines quote the taught rule lines — verbatim-rule doctrine, A3-derived whitelist clears them; element-free, digit-free) · mcq4
A poster summarizing the metal package lists four property lines. One of the lines is wrong. Which line is the mistake?
Metals shatter when hammered. KEY
Metals are shiny.
Metals conduct heat well.
Metals can be drawn into wires.
PTB-019 · easy · recall · seq 2 · authored (never-found-uncombined occurrence facet, rule line 7 — pool 34's key FACT restructured into a direct how-found stem with a substantive positive key, all-fresh options; element-free; misconception classes = unreactive-metal behavior / invented protected deposit / reactivity-swapped-for-rarity) · mcq4
In nature, how are the alkali metals found?
Always combined with other elements — never as pure metal. KEY
As shiny pure-metal nuggets, the way unreactive metals can occur.
As pure metal, but only deep underground where air and water never reach.
Combined with other elements, but only in a handful of rare minerals.
PTB-023 · easy · recall · seq 3 · authored (salts-with-metals case on a what-should-you-expect surface — the stem asserts no outcome, so the switch-off distractor stays consistent; element-free, digit-free; taught misconception classes from fluency-2) · mcq4
A bit of metal is dropped into a jar filled with a pure halogen. What should you expect the two elements to do?
React — the product is one of the salts halogens form with metals. KEY
Mix together into a loose mixture that could be taken back apart unchanged.
React — but the product is a brand-new metal.
Do nothing — halogens leave metals unchanged.
PTB-027 · easy · recall · seq 4 · authored (D8 colorful-compounds trait read; key = rule line 3 VERBATIM, verbatim-rule doctrine; distractors = color-removal class (fluency-1 distractor lexicon, a whitelist source), metal-look transfer, and the no-compounds noble-gas confusion; element-free, digit-free — no copper/patina reuse, the article's instance stays the article's) · mcq4
Which statement about the compounds of the transition metals is correct?
Many transition metals form colorful compounds. KEY
Their compounds keep the silvery, metallic look of the metals themselves.
The compounds' colors fade away once the compounds dry out.
The colors come from bits of unreacted metal trapped inside the compounds.
PTB-009 · medium · application · seq 5 · authored (brittle-clause observation per the blueprint seq-5 contract: fresh observation-to-property link on an unnamed solid nonmetal; option set = the lesson's designed package-clause grid, seed-A structure with a different key; element-free) · mcq4
A technician taps a solid sample of a nonmetal element against the edge of a workbench, and the sample breaks apart into sharp fragments instead of denting. Which part of the nonmetal package does that show?
Solid nonmetals are brittle. KEY
Solid nonmetals flatten into thin sheets when struck.
Solid nonmetals shine like polished metal.
Solid nonmetals conduct electricity well.
PTB-011 · medium · application · seq 6 · seed:pool[11] (PTB-011 gateItems[2]; stem/key/distractors b,c/explanation/figureSpec VERBATIM; NOTA seat d REPLACED with the class-hedge blend per replace_distractor [ANSWERS #2] — RECORD FOR DAVID_REVIEW; explanation = seed text + one dispatch sentence; figure payload carried so blind packets are self-contained) · mcq4
The property card for element E is shown. Classify element E.
FIGURE (data-table · stimulus) — title: "Element E" · columns: ["Property", "Measured result"] · rows: [["state at room temperature", "gas"], ["color", "colorless"], ["conducts electricity", "no"]] · style: "small property card"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "data-table",
  "title": "Element E",
  "columns": [
   "Property",
   "Measured result"
  ],
  "rows": [
   [
    "state at room temperature",
    "gas"
   ],
   [
    "color",
    "colorless"
   ],
   [
    "conducts electricity",
    "no"
   ]
  ],
  "style": "small property card"
 }
}
A nonmetal. KEY
A metal.
A metalloid.
Both a metal and a nonmetal.
PTB-013 · medium · application · seq 7 · seed:U3-G2/pool[17] (PTB-013 gateItems[2]) — stem, key, distractors b/c + feedback, both explanations, and figureSpec byte-VERBATIM; single edit = flagged replace_distractor: NOTA fourth seat -> 'A transition metal.' (the transition-sounds-like-in-between conflation, the exact trap for a boundary cell; key is METALLOID so this is NOT the banned defensible-when-key-is-metal case — no stair-step cell is a center-block metal) · mcq4
A cell is marked on the table outline, sitting exactly on the stair-step line, partway down the zigzag. Classify the element that lives there.
FIGURE (periodic-table-regions · stimulus) — shadedRegions: [] · regionLabels: false · stairStep: true · markedCells: [{"label": "Y", "position": "on the stair-step line, middle of the zigzag"}] · style: "unshaded outline, stair-step drawn, one unlabeled cell marked Y"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-regions",
  "shadedRegions": [],
  "regionLabels": false,
  "stairStep": true,
  "markedCells": [
   {
    "label": "Y",
    "position": "on the stair-step line, middle of the zigzag"
   }
  ],
  "style": "unshaded outline, stair-step drawn, one unlabeled cell marked Y"
 }
}
A metalloid. KEY
A metal.
A nonmetal.
A transition metal.
PTB-015 · medium · application · seq 8 · authored (James's PTB-015 period-read template kept verbatim-parallel; fresh instance: bismuth, Period 6 -> 6 — preserves the seed row's deep-period case after the form-A freshen, and James's 'however deep the row' clause is reused here where it is true; zero occurrences anywhere in the scope corpus and not a MATERIALS word; chosen over lead deliberately — 'lead' sits in PTB-014's corpus and in MATERIALS) || QC-PATCH stage-3 wave-1: re-instanced bismuth->thallium (C#8<->D#9 cross-form gram + duplicate-instance telegraph; thallium has zero spec occurrences) · numeric
Thallium sits in Period 6 of the periodic table. How many occupied electron shells does a thallium atom have?
Answer: 6 shells KEY
also accepted: 6 shells, 6.0
wrongValueDiagnostics
[
 {
  "value": 13,
  "misconception": "you used thallium's group instead of its period — the row gives the shell count",
  "feedback": "This answer is wrong — 13 is thallium's group number. The row, not the column, gives the shell count: thallium sits in Period 6, so a thallium atom has six occupied shells."
 },
 {
  "value": 3,
  "misconception": "you subtracted 10 from the group number — that move belongs to a different reading, and the shell count is simply the period",
  "feedback": "This answer is wrong — 3 comes from subtracting 10 from thallium's group number, and that move belongs to a different reading. The shell count is simply the period: thallium sits in Period 6, so a thallium atom has six occupied shells."
 }
]
feedback
{
 "keyExplanation": "Thallium is a main-group element in Period 6. The period number equals the number of occupied shells — however deep the row. A thallium atom has six occupied shells.",
 "anticipatedWrong": [
  {
   "value": 13,
   "misconception": "you used thallium's group instead of its period — the row gives the shell count",
   "feedback": "This answer is wrong — 13 is thallium's group number. The row, not the column, gives the shell count: thallium sits in Period 6, so a thallium atom has six occupied shells."
  },
  {
   "value": 3,
   "misconception": "you subtracted 10 from the group number — that move belongs to a different reading, and the shell count is simply the period",
   "feedback": "This answer is wrong — 3 comes from subtracting 10 from thallium's group number, and that move belongs to a different reading. The shell count is simply the period: thallium sits in Period 6, so a thallium atom has six occupied shells."
  }
 ]
}
PTB-016 · medium · application · seq 9 · authored (James's PTB-016 mapping-item structure kept verbatim-parallel; fresh instance: boron — literal wave-3 classroom-set member, NOT a MATERIALS-lexicon word, in NO scope lesson's corpus blob (22-lesson check; PTB-010's metalloid territory untouched: the stem asks only the group->valence mapping, no class claims); shallow period named so the period-read trap has a defined value, mirroring the tin seed's design; group spelled 'Thirteen' per this row's recorded digit-free pattern) · numeric
Boron sits in Group Thirteen of the periodic table, in Period 2. How many valence electrons does a boron atom have?
Answer: 3 valence electrons KEY
also accepted: 3 valence electrons, three, 3.0
wrongValueDiagnostics
[
 {
  "value": 13,
  "misconception": "you gave the group number itself — for Groups 13 through 18, subtract 10",
  "feedback": "This answer is wrong — 13 is the group number itself. For Groups 13 through 18, the group number minus 10 gives the count: 13 − 10 = 3, so a boron atom has three valence electrons."
 },
 {
  "value": 2,
  "misconception": "you used boron's period instead of its group — the column gives the valence count",
  "feedback": "This answer is wrong — 2 is boron's period. The column, not the row, gives the valence count: boron sits in Group 13, and 13 − 10 = 3, so a boron atom has three valence electrons."
 }
]
feedback
{
 "keyExplanation": "Boron is a main-group element in Group 13. Groups 13 through 18 give the group number minus 10: 13 − 10 = 3. The period changes nothing — a boron atom has three valence electrons.",
 "anticipatedWrong": [
  {
   "value": 13,
   "misconception": "you gave the group number itself — for Groups 13 through 18, subtract 10",
   "feedback": "This answer is wrong — 13 is the group number itself. For Groups 13 through 18, the group number minus 10 gives the count: 13 − 10 = 3, so a boron atom has three valence electrons."
  },
  {
   "value": 2,
   "misconception": "you used boron's period instead of its group — the column gives the valence count",
   "feedback": "This answer is wrong — 2 is boron's period. The column, not the row, gives the valence count: boron sits in Group 13, and 13 − 10 = 3, so a boron atom has three valence electrons."
  }
 ]
}
PTB-017 · medium · application · seq 10 · seed:U3-G2/pool[29] (= PTB-017 gateItems[2], James) — VERBATIM; zero placement flags; element-free and digit-free in all scanned fields, so it sits clean above C#11's O/S/Se (the blueprint's stated reason for parking pool 30 on C); the period-contrast tests the mechanism without touching PTB-018's across-table repetition (PTB-017 specNotes); d3 = substantive claim-DENIAL seat, NOT V-T5 NOTA — blind-review watch note recorded · mcq4
Elements sitting side by side in Period 3 usually do NOT behave alike. Why not?
The valence count changes at every step across that period, and valence electrons set the behavior. KEY
Because their atomic masses are too similar.
Because they have different numbers of occupied shells.
They do behave alike — any two neighboring elements in the table match in behavior.
PTB-018 · medium · application · seq 11 · seed:U3-G2/pool[30] (= PTB-018 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_scope_article flag (oxygen/selenium/sulfur) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates; placed C per stage 1 (off A: A#5 oxygen; off B: B#10 O/S adjacency at seq 10/11); the seed's selenium (Period 4) is James's instance — the Periods-2-3 constraint binds authored forms only · mcq4
Oxygen, sulfur, and selenium behave in similar ways, and the same behavior keeps coming back as you read along the atomic-number list. What explains the pattern's return?
Every period restarts the valence-electron count, so the six-electron point comes around once in each period. KEY
The three elements are built of identical atoms, so the same behavior appears wherever they sit.
Their atomic masses climb by the same fixed amount each time, and equal mass steps bring the behavior back.
The number of occupied shells is the same for all three.
PTB-020 · medium · application · seq 12 · seed:U3-G2/pool[38] (= PTB-020 gateItems[2]) — VERBATIM (formatting-only: <p> strip + house feedback composition). Placement flag CARRIED: freshness_scope_article(rubidium) — informational only at stage 3 (rubidium is not in the validator's MATERIALS lexicon). DETERMINISTIC STAGE-3 V-T7 FOOTPRINT measured and pinned (rows/_check_row12.py): own-lesson taught-material 'water' (spec_mats[PTB-020] = {air, water}; water IS the lesson's taught reaction medium and this check is the specNotes-designed rubidium water check); cross-form substance 'water' vs the placed water-bearing A-form seeds A#13 (pool 40), A#18 (pool 43), A#20 (pool 63); within-form C#18 (pool 44, water) is NON-adjacent -> validator WARN class. Same resolution class as form B (recorded adjudicated_instance_families + U2-G2-class wrapper at assembly). The seat-c feedback 'you made it a nuclear event' keeps its stage-1 recorded scan adjudication: a chemical-vs-nuclear-change misconception correction in a FEEDBACK field, not a scenario framing (wave-3 binding instance rule targets scenario framings; the token is also outside the banned-token regex). || QC-PATCH stage-3 wave-1: medium water->air (C#12/C#13 within-form adjacency, QB sec.5 — never wrapper-excusable; PTB-020 teaches the air axis alongside water and the MECH-METAL-LOSS check is medium-independent; realism: rubidium is pyrophoric in air) · mcq4
A pellet of rubidium, cut open moments ago, can catch fire on its own in open air. At the level of one rubidium atom, what starts the trouble?
The atom gives away its single, easily removed valence electron. KEY
The atom pulls in an extra electron from the air.
The atom's nucleus breaks apart when air touches it.
The atom drifts off unchanged and simply mixes into the air.
PTB-021 · medium · application · seq 13 · authored (concrete two-sample discrimination on the taught axes — less-vigorous pace + greater hardness; the blueprint's steadier-reaction/harder-metal contract applied to unlabeled samples; element-free; option grid = the lesson's designed misconception classes: flipped-comparison, family-merge, switched-off) · mcq4
Two unlabeled metal samples are tested behind a safety shield. Sample 1 reacts violently the instant it meets the water, and a blunt blade sinks into its surface with little effort. Sample 2 gives off a steady trickle of bubbles in water, and the blade will not bite into it. Which conclusion do the two family profiles support?
Sample 2 is the alkaline earth metal — its steadier reaction and harder metal fit the Group 2 profile. KEY
Sample 1 is the alkaline earth metal — the more vigorous water reaction always marks the Group 2 family.
Both samples are alkaline earth metals, because every water-reactive metal belongs to Group 2.
Neither sample is an alkaline earth metal, because alkaline earth metals show no reaction with water.
PTB-024 · medium · application · seq 14 · seed:U3-G2/pool[50] (= PTB-024 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; no NOTA/AOTA; flags freshness_same_lesson (chlorine — article-FIGURE recurrence only per specNotes) + freshness_scope_article (iron) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates · mcq4
Chlorine gas passes over hot iron, and the two react quickly. During the reaction, which way do electrons move?
From the iron atoms to the chlorine atoms. KEY
From the chlorine atoms to the iron atoms.
Back and forth — each atom repeatedly gives and retakes the same electron.
No electrons move — the atoms only mix together.
PTB-025 · medium · application · seq 15 · authored (why-protect long-term per the blueprint seq-15 contract: historic document sealed in a Group 18 case — real archival practice; element-free, gas unnamed; chlorine-free per the blueprint's C#15 note; surface shares nothing with C#14's chlorine-over-hot-iron or C#16's radon claim) · mcq4
The original copy of a historic charter is displayed in a sealed case that has been filled with a noble gas instead of ordinary air. Why does that filling help the document last?
The gas almost never reacts, so it leaves the paper and ink chemically alone, while the reactive gases in ordinary air would slowly attack them. KEY
The gas reacts gently with the paper's surface, sealing the whole document under a thin protective skin that ordinary air could never have formed.
The gas forms salts with the case's metal frame, and the salts trap anything harmful before it reaches the document.
The gas outweighs ordinary air, pressing any harmful gases out through the seams of the case before they can settle.
PTB-026 · medium · application · seq 16 · seed:U3-G2/pool[56] (= PTB-026 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_scope_article flag (radon) carried; electron-count framing only, no radiation language (wave-3 binding instance rule satisfied — stage-1 scan adjudication); 'The student is right' seat = claim-evaluation option, substantive, NOT NOTA — blind watch. STAGE-3 WATCH: seed key is the form's longest option (107 vs 63/74/97) — if V-T4 fails, re-word DISTRACTORS, log as seed deviation · mcq4
A student argues: 'Radon should react easily, because with so many electrons it always has spares to give.' Why is the student wrong?
Reactivity follows the outer shell, and radon's is full — little tendency to lose electrons, spares or not. KEY
The student is wrong only because radon has very few electrons.
The student is right — atoms with more electrons are always more reactive.
The student is wrong because radon's inner electrons, not its outer ones, do all of its reacting.
PTB-014 · hard · transfer · seq 17 · authored (fresh 12/13-boundary pair per the blueprint seq-17 contract: cadmium/indium — real Period-5 next-door columns, both corpus-clean instances disjoint from every C-form seeded element; four assignment permutations, the seed's proven structure with a fresh pair and re-anchored feedback) · mcq4
Cadmium occupies Group 12, and indium occupies Group 13, one column to the right. Classify each of the two.
Cadmium: a transition metal. Indium: a main-group element. KEY
Both are transition metals.
Both are main-group elements.
Cadmium: a main-group element. Indium: a transition metal.
PTB-022 · hard · transfer · seq 18 · seed:U3-G2/pool[44] (= PTB-022 gateItems[2], James) — VERBATIM: stem, key, all three distractors, feedback, and explanations; freshness_scope_article flags (barium, cesium) carried from seed_placement, no fix applied per seed doctrine — stage-3 validator arbitrates; placed on C per seed_placement to avoid pairing with B#13's Ba/Cs seed; V-T4 clean (distractor c is the longest) · mcq4
Cesium and barium are Period 6 neighbors. Water dropped onto each produces a violent burst from one and a strong but slower fizz from the other. Which is which, and why?
Cesium bursts and barium fizzes — cesium's single valence electron takes less energy to remove than barium's two. KEY
Barium bursts and cesium fizzes — barium's two electrons double its reaction.
Cesium bursts and barium fizzes — but only because barium's atoms are heavier and heavier atoms always react more slowly.
The two behave identically, so the difference must come from the water used.
PTB-028 · hard · transfer · seq 19 · authored (blueprint seq-19 contract: fresh unhandled-element prediction — astatine, never seen by any classroom, from iodine's known reaction with silver; halogen swap downward with a NON-family partner fixed, pool-61's sulfur-stays-fixed logic on the halogen side; fresh pairings Ag+I and Ag+At — silver astatide is documented tracer chemistry, the same evidence grade as the seed's francium iodide; silver = wave-3 classroom set + PTB-008/027 scope WARN class; placed on C after the parallel-authoring swap — see the collision note) · mcq4
Silver and iodine react to form silver iodide. Astatine sits at the bottom of iodine's group, and it is so scarce that no chemistry classroom has ever seen a sample. Which prediction does the family pattern justify?
Silver would react with astatine to form silver astatide. KEY
Silver would react with astatine to form astatine iodide.
No prediction is possible for an element that no class has ever had a sample of.
Silver would react with astatine to form silver iodide.
PTB-029 · hard · transfer · seq 20 · authored (Group 17 predict-the-kind per the blueprint contract: fluorine, first-time-handling surface — fluorine has ZERO placements gate-wide and is never a pool-seed subject at the profile angle (pool 64's halogen subject is bromine, spared); 'Fluorine belongs to Group 17' dodges PTB-028's WE token run 'Fluorine sits in'; options = parallel reason-free family profiles, transplant grid re-worded from pool 64's; C#14's chlorine is a different halogen at a different angle — noted, distinct elements) · mcq4
A specialty lab is preparing to handle fluorine for the first time. Fluorine belongs to Group 17. Judged by its family, what kind of element should the lab expect?
A very reactive nonmetal that travels as two-atom molecules and forms salts with metals. KEY
A soft, shiny metal that attacks water on contact and is never found uncombined in nature.
A colorless gas that almost never joins any reaction.
A hard, dense metal, a good conductor, known for colorful compounds.
PTB-029 · medium · application · seq 21 · authored (blueprint rows[20] seq-21 AUTHORED-FRQ directive; instance = potassium with Group 1 supplied on a stockroom order-form surface; part (c) account = the PTB-020 easy single-electron give-away) · frq
A stockroom order form requests a small sample of potassium, and the catalog entry supplies just one detail beside the name: Group 1. The stockroom manager wants to know what to expect before the sample arrives.
A stockroom order form requests a small sample of potassium, and the catalog entry supplies just one detail beside the name: Group 1. The stockroom manager wants to know what to expect before the sample arrives. (a) Using only the group number in the catalog entry, name the chemical family potassium belongs to, and state how you can tell from that one detail. (b) Predict two ways potassium should behave. Each prediction must be a behavior potassium's whole family shares, stated as a prediction about potassium itself. (c) Explain why potassium's family is so reactive, in terms of the atoms' valence electrons.
Part a. Using only the group number in the catalog entry, name the chemical family potassium belongs to, and state how you can tell from that one detail.
Model: Group 1 names the alkali metals — hydrogen at the top of the group is the one non-member, and potassium is not hydrogen. So potassium is an alkali metal — the group number in the catalog gives the family by itself, with no periodic-table lookup needed. Answer: Potassium is an alkali metal — Group 1 names the alkali-metal family (hydrogen is the group's one non-member, and potassium is not hydrogen).
Part b. Predict two ways potassium should behave. Each prediction must be a behavior potassium's whole family shares, stated as a prediction about potassium itself.
Model: The taught alkali profile: a soft metal — soft enough to cut with a table knife; shiny when fresh, but the surface dulls quickly in open air; reacts vigorously with water; so reactive that none of the family is ever found uncombined in nature. Any two, applied to potassium — for example: the potassium sample should be soft enough to cut with a knife, and it should react vigorously if it touches water. Also acceptable: a freshly cut surface should be shiny but dull quickly in open air; and the sample will not have been dug up as a pure lump — expect it delivered sealed away from air and water, since the family is never found uncombined. Not acceptable: a ranking against another alkali metal — which member reacts fastest is not part of the taught profile. Answer: Any two of: soft enough to cut with a knife; shiny when fresh but quick to dull in open air; reacts vigorously with water; never found uncombined (so expect it sealed away from air and water) — each stated as a prediction about potassium.
Part c. Explain why potassium's family is so reactive, in terms of the atoms' valence electrons.
Model: A metal atom reacts by giving away its outer electrons, and it reacts more easily when those electrons are easier to remove. An alkali metal atom has a single valence electron, and that one outer electron is easy to remove. With its one valence electron given away so easily, a potassium atom reacts quickly — the easy give-away is what makes the whole family so reactive. Answer: An alkali metal atom has a single valence electron that is easy to remove; the atom gives it away quickly, and that easy give-away is why the family is so reactive.
Full model answer. (a) Group 1 names the alkali metals — hydrogen at the top of the group is the one non-member, and potassium is not hydrogen. So potassium is an alkali metal — the group number in the catalog gives the family by itself, with no periodic-table lookup needed. Answer: Potassium is an alkali metal — Group 1 names the alkali-metal family (hydrogen is the group's one non-member, and potassium is not hydrogen). (b) The taught alkali profile: a soft metal — soft enough to cut with a table knife; shiny when fresh, but the surface dulls quickly in open air; reacts vigorously with water; so reactive that none of the family is ever found uncombined in nature. Any two, applied to potassium — for example: the potassium sample should be soft enough to cut with a knife, and it should react vigorously if it touches water. Also acceptable: a freshly cut surface should be shiny but dull quickly in open air; and the sample will not have been dug up as a pure lump — expect it delivered sealed away from air and water, since the family is never found uncombined. Not acceptable: a ranking against another alkali metal — which member reacts fastest is not part of the taught profile. Answer: Any two of: soft enough to cut with a knife; shiny when fresh but quick to dull in open air; reacts vigorously with water; never found uncombined (so expect it sealed away from air and water) — each stated as a prediction about potassium. (c) A metal atom reacts by giving away its outer electrons, and it reacts more easily when those electrons are easier to remove. An alkali metal atom has a single valence electron, and that one outer electron is easy to remove. With its one valence electron given away so easily, a potassium atom reacts quickly — the easy give-away is what makes the whole family so reactive. Answer: An alkali metal atom has a single valence electron that is easy to remove; the atom gives it away quickly, and that easy give-away is why the family is so reactive.

Form D

PTB-008 · easy · recall · seq 1 · authored (package case rotated onto a fix-the-notebook surface for the conduction pair; key = PTB-008 rule line 2 VERBATIM per the verbatim-rule doctrine for fact-atom recall keys — every key gram is an A3-derived rule-line whitelist entry; element-free, digit-free) · mcq4
A student's notebook reads: 'Metals let electricity pass through but block heat.' What does the metal package actually say?
Metals conduct heat well and conduct electricity well. KEY
Metals conduct electricity well but block heat from passing.
Metals conduct heat well but block electricity from passing.
Metals block both heat and electricity from passing through.
PTB-019 · easy · recall · seq 2 · authored (under-oil storage facet = the HOOK scenario rotated sodium -> potassium; potassium = rule-line family member, recorded stage-3 V-T7 adjudication candidate under the family-atom exception; misconception classes = cosmetic-protection (the hook's own 'not to keep it clean' contrast) / made-it-a-vapor / shape-sag, fresh wording) · mcq4
In a school stockroom, a jar of potassium is kept sealed, with the metal sitting under a layer of oil. What is the oil for?
Potassium reacts readily with the air, and the oil keeps the air off the metal. KEY
The oil keeps stray grit from scratching the metal's shiny surface.
Potassium would escape as a vapor from an open jar without the oil on top.
Potassium is so soft that without the oil the piece would lose its shape.
PTB-023 · easy · recall · seq 3 · authored (whole-profile -> family-name identification; element-free, digit-free; options are R11-parallel bare family labels — A1 class, runtime-derived; key needs only PTB-023 content, V-T11 clean) · mcq4
A reference book sums up one element family this way: very reactive nonmetals, traveling as two-atom molecules, and forming salts with the metals they meet. Which family is being described?
The halogens. KEY
The noble gases.
The alkali metals.
The transition metals.
PTB-027 · easy · recall · seq 4 · authored (D8 cross-family contrast read — PTB-027 extraNotes: the hard-vs-knife-soft contrast with Group 1 is fair game, both profiles prior; 'typical' hedge retained; element-free, only the ignored digit 1 appears) · mcq4
Compared with a Group 1 metal, what should a typical transition metal be like?
Noticeably harder and denser than the Group 1 metal. KEY
Softer and lighter than the Group 1 metal.
Identical in hardness, because all metals feel the same.
Brittle and crumbly, unlike the Group 1 metal.
PTB-009 · medium · application · seq 5 · authored (electrical-conduction clause per the blueprint seq-5 contract: predict + why in a battery-and-bulb circuit, mirroring the seed-B predict-and-why shape on the package's other conduction; element-free; the one real-world exception, graphite, is banned from the course's instance set — PTB-009 specNotes) · mcq4
A bar of a solid nonmetal element is clipped into a battery-and-bulb circuit in place of one of the metal wires. Compared with the metal wire, what should the bulb do, and why?
Glow far more weakly, if at all, because nonmetals conduct electricity poorly. KEY
Light just as brightly, because every solid element carries current well.
Light up only once the bar warms, because warmth turns a nonmetal into a good conductor.
Flicker on and off, because a brittle solid carries current in short bursts.
PTB-011 · medium · application · seq 6 · authored (NONE-VS-WEAK boundary, nonmetal side: one-feature flip from pool[9] — conduction weak -> none flips the key metalloid -> nonmetal; foils = pool[9]'s shine-decides family, the shiny-brittle-metalloid rounding-up family [star distractor], and the dual-membership blend class) · mcq4
An element forms bright, mirror-shiny crystals, yet it shatters at a light hammer tap and conducts no electricity — not even on a sensitive meter. Classify it.
A nonmetal. KEY
A metal.
A metalloid.
An alloy of a metal and a nonmetal.
PTB-013 · medium · application · seq 7 · authored (left-side metal clause — the seeds test only the CENTER metal read; unnamed cell, pure position transfer per PTB-013 specNotes; element-free, digit-free; marked cell 'well below the column's top cell' so the hydrogen top-left cell is geometrically excluded, D1 honored; fourth seat = 'A halogen.' reactive-family home swap — 'An alkali metal.' forbidden here as defensible-TRUE for a left-column cell, 'A transition metal.' avoided since the key is metal per the blueprint ban) · mcq4
A cell is marked on the table outline, in the leftmost column, about halfway down — well below the column's top cell. Classify the element that lives there.
FIGURE (periodic-table-regions · stimulus) — shadedRegions: [] · regionLabels: false · stairStep: true · markedCells: [{"label": "X", "position": "leftmost column, about halfway down — well below the column's top cell"}] · style: "unshaded outline, stair-step drawn, one unlabeled cell marked X"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-regions",
  "shadedRegions": [],
  "regionLabels": false,
  "stairStep": true,
  "markedCells": [
   {
    "label": "X",
    "position": "leftmost column, about halfway down — well below the column's top cell"
   }
  ],
  "style": "unshaded outline, stair-step drawn, one unlabeled cell marked X"
 }
}
A metal. KEY
A nonmetal.
A metalloid.
A halogen.
PTB-015 · medium · application · seq 8 · authored (James's PTB-015 period-read template kept verbatim-parallel; fresh instance: boron, Period 2 -> 2; literal classroom-set member; boron token occurs in PTB-013/PTB-018 corpus but boron is not a MATERIALS-lexicon word and the focused gram scan is clean; ledger: row07's authored D marked-cell position must not mark boron's cell) · numeric
Boron sits in Period 2 of the periodic table. How many occupied electron shells does a boron atom have?
Answer: 2 shells KEY
also accepted: 2 shells, 2.0
wrongValueDiagnostics
[
 {
  "value": 13,
  "misconception": "you used boron's group instead of its period — the row gives the shell count",
  "feedback": "This answer is wrong — 13 is boron's group number. The row, not the column, gives the shell count: boron sits in Period 2, so a boron atom has two occupied shells."
 },
 {
  "value": 3,
  "misconception": "you subtracted 10 from the group number — that move belongs to a different reading, and the shell count is simply the period",
  "feedback": "This answer is wrong — 3 comes from subtracting 10 from boron's group number, and that move belongs to a different reading. The shell count is simply the period: boron sits in Period 2, so a boron atom has two occupied shells."
 }
]
feedback
{
 "keyExplanation": "Boron is a main-group element in Period 2. The period number equals the number of occupied shells. A boron atom has two occupied shells.",
 "anticipatedWrong": [
  {
   "value": 13,
   "misconception": "you used boron's group instead of its period — the row gives the shell count",
   "feedback": "This answer is wrong — 13 is boron's group number. The row, not the column, gives the shell count: boron sits in Period 2, so a boron atom has two occupied shells."
  },
  {
   "value": 3,
   "misconception": "you subtracted 10 from the group number — that move belongs to a different reading, and the shell count is simply the period",
   "feedback": "This answer is wrong — 3 comes from subtracting 10 from boron's group number, and that move belongs to a different reading. The shell count is simply the period: boron sits in Period 2, so a boron atom has two occupied shells."
  }
 ]
}
PTB-016 · medium · application · seq 9 · authored (James's PTB-016 mapping-item structure kept verbatim-parallel; fresh instance: bismuth — standard stable classroom sample, NOT a MATERIALS-lexicon word, in NO scope lesson's corpus blob (22-lesson check); deep period named so the tin seed's 'deep period changes nothing' case is retested on a fresh surface; group spelled 'Fifteen' per this row's recorded digit-free pattern) · numeric
Bismuth sits in Group Fifteen of the periodic table, in Period 6. How many valence electrons does a bismuth atom have?
Answer: 5 valence electrons KEY
also accepted: 5 valence electrons, five, 5.0
wrongValueDiagnostics
[
 {
  "value": 15,
  "misconception": "you gave the group number itself — for Groups 13 through 18, subtract 10",
  "feedback": "This answer is wrong — 15 is the group number itself. For Groups 13 through 18, the group number minus 10 gives the count: 15 − 10 = 5, so a bismuth atom has five valence electrons."
 },
 {
  "value": 6,
  "misconception": "you used bismuth's period instead of its group — the column gives the valence count",
  "feedback": "This answer is wrong — 6 is bismuth's period. The column, not the row, gives the valence count: bismuth sits in Group 15, and 15 − 10 = 5, so a bismuth atom has five valence electrons. The deep period changes nothing."
 }
]
feedback
{
 "keyExplanation": "Bismuth is a main-group element in Group 15. Groups 13 through 18 give the group number minus 10: 15 − 10 = 5. The deep period changes nothing — a bismuth atom has five valence electrons.",
 "anticipatedWrong": [
  {
   "value": 15,
   "misconception": "you gave the group number itself — for Groups 13 through 18, subtract 10",
   "feedback": "This answer is wrong — 15 is the group number itself. For Groups 13 through 18, the group number minus 10 gives the count: 15 − 10 = 5, so a bismuth atom has five valence electrons."
  },
  {
   "value": 6,
   "misconception": "you used bismuth's period instead of its group — the column gives the valence count",
   "feedback": "This answer is wrong — 6 is bismuth's period. The column, not the row, gives the valence count: bismuth sits in Group 15, and 15 − 10 = 5, so a bismuth atom has five valence electrons. The deep period changes nothing."
  }
 ]
}
PTB-017 · medium · application · seq 10 · authored (direct-why case on an UNNAMED same-column top/bottom pair — the seed-B pattern with the matching observation supplied in the stem and the pair left element-free; digit-free; 'main-group' qualifier keeps the valence-count claim inside the course's dimmed-middle-block discipline; key clause reuses the rule-line reason wording per the verbatim-reason doctrine (runtime A3); distractor classes = taught shell-swap / size-mass / total-electron misconceptions, fresh wording re-anchored to the column geometry) · mcq4
Two main-group elements sit in the same column of the periodic table — one high in the column, the other far below it. Lab tests show that, given the same partner element, each of the two forms the same kind of compound with it. Which shared feature of their atoms accounts for the matching chemistry?
Their atoms have the same number of valence electrons — the electrons that take part when atoms react. KEY
Their atoms have the same number of occupied electron shells, so both are built on the same set of shells.
Their atoms are close matches in size and in mass, which is what makes their compounds come out matching.
Their atoms hold the same total number of electrons, counted across all of their shells.
PTB-018 · medium · application · seq 11 · authored (mark-the-list pattern prediction per the facet rotation: WE2's task class rotated to a fresh count/instance/surface — silicon, four-electron step, writes-out-and-circles over Periods 2-3; silicon owned by this row on form D (ownership watch in notes); pool 32's carbon/silicon PAIR and its behaves-like->conclude-count angle left with the spare; misconception classes = mass-multiples / period-as-one-block / same-shells-behave-alike, fresh wording) · mcq4
Silicon's atoms have four valence electrons. A student writes out the sixteen elements of Periods 2 and 3 in one long row, in order of atomic number, and circles every element whose behavior matches silicon's. What circling pattern shows up, and why?
One circle in each period, sitting at the four-electron step, because each period runs through the count of four just once. KEY
Circles at every element whose atomic mass lands close to a multiple of silicon's, because behavior returns with each fixed step up in mass.
Circles covering every element of Period 3 from start to finish, because silicon's whole period behaves together as one block.
Circles on every element with three occupied shells, because atoms carrying the same number of shells behave the same way.
PTB-020 · medium · application · seq 12 · authored (ION-FORMATION account: the setup's recap 'an atom which loses an electron becomes an ion' + the extraNotes license 'ion vocabulary (ATM-060) may be leaned on but no charges are computed' — no charge appears anywhere; element-free, air/water-free, digit-free, so the form adds ZERO V-T7 footprint; foils = the lesson's designed misconception grid: direction reversal [fluency-1 d1 class], emptied-atom [fluency-1 d2 class], split-atom [fluency-1 d3 class], each re-worded and re-anchored to the ion surface) · mcq4
When a piece of an alkali metal reacts, each of its atoms ends up as an ion. Which change turns one of these metal atoms into an ion?
It gives away its single valence electron, and losing that electron is what makes it an ion. KEY
It pulls an extra electron in from its surroundings.
It gives away every electron it has, from the outer shell inward.
It breaks apart into two smaller atoms, and each of the smaller pieces then counts as one ion.
PTB-021 · medium · application · seq 13 · authored (correct-the-claim on the same taught axes: water reactivity alone cannot separate the two reactive-metal families — the steady pace and hardness point to Group 2; element-free; b's 'Nothing is wrong' = substantive claim-evaluation seat, pool-31/43 class, blind-review watch recorded, not V-T5 NOTA) · mcq4
A test piece from an unlabeled jar of silvery metal keeps up a slow, steady fizz in the water for several minutes, and the piece is noticeably hard. A student concludes: 'It reacts with water, so it has to be an alkali metal.' What is wrong with the student's conclusion?
Water reactivity fits both reactive-metal families — the steady pace and the hardness point to an alkaline earth metal instead. KEY
Nothing is wrong — the alkali metals are the only metals that react with water.
The conclusion is wrong, but only because alkali metals never react in water.
Nothing can be concluded from the test, because the two water-reactive metal families behave identically in water and cannot be told apart.
PTB-024 · medium · application · seq 14 · authored (claim correction of the REVERSED gain direction per the blueprint seq-14 contract: the student casts the halogen as a giver with the correct seven-count; element-free; option c 'Nothing is wrong' = substantive claim-evaluation seat, pool 31/43 class, blind-review watch note recorded — NOT V-T5 NOTA) · mcq4
A student explains halogen reactivity: 'When a halogen atom reacts, it hands one of its seven outer electrons over to the other atom.' What is wrong with the account?
The direction is backward — a halogen atom keeps all seven of its outer electrons and pulls in the one it is missing. KEY
Only the number is off — when it reacts, a halogen atom actually hands over all seven of its outer electrons at once.
Nothing is wrong — handing electrons over is how every reactive atom, metal or nonmetal, behaves.
The count is the error — a halogen atom holds just one outer electron, so one electron is all it could hand over.
PTB-025 · medium · application · seq 15 · authored (explain-the-aftermath per the blueprint seq-15 contract: Group 18 fire-suppression flood leaves circuits chemically untouched — real inert-gas fire-control practice; element-free, gas unnamed; the physical smothering is SUPPLIED by the stem so only the chemical inaction is tested; hot-metal/welding surfaces deliberately avoided row-wide) · mcq4
One kind of fire-control system floods a computer room with a noble gas, smothering the flames by crowding out the air. Afterward, technicians find no corrosion or other chemical damage on any circuit. Why did a roomful of the gas leave the circuits chemically untouched?
The gas almost never reacts, so it touched every part of every circuit without chemically changing any of it. KEY
The gas was used up reacting with the flames as it put them out, so none was left to reach the circuits.
The gas laid down a thin protective coating over every circuit board, shielding the metal from the fire's fumes.
The gas is a poor conductor of electricity, so it blocked stray currents from reaching and damaging the circuits.
PTB-026 · medium · application · seq 16 · authored (application-why per the blueprint seq-16 contract, mirroring the seed-A sealed-enclosure surface on a fresh scene: archival document sealed under a Group 18 gas; element-free — the gas is named only by group, the pool-52 pattern; cross-row scenario-dedup watch vs row15's authored applications recorded in authoring_notes) || QC-PATCH stage-3 wave-1: de-aired + scenario moved charter->tapestry (D#15/D#16 adjacency + C#15 same-scenario cross-form telegraph) · mcq4
An archive stores a fragile medieval tapestry in a sealed display case flooded with a noble gas. Decade after decade the gas presses against the ancient threads, yet it never attacks them. Why not?
Its atoms' outer shells are full, giving them little tendency to gain, lose, or share electrons, so no attack ever starts. KEY
Its atoms are each one electron short of full, and the threads cannot supply the missing electron.
Its atoms handed their outer electrons over to the case walls when it was sealed, leaving nothing behind that could react with the cloth.
Its particles spread so far apart as a gas that they never actually touch the tapestry inside the case.
PTB-014 · hard · transfer · seq 17 · authored (which-of-four bare-element transfer per the blueprint seq-17 contract and specNotes — 'which-one-of-four items carry most of the assessment'; figureless LISTED-with-group-numbers framing, never the fluency marked-cells figure idiom; key = the transition metal; hard band via boundary traps: beryllium at Group 2 and boron at Group 13 sit one column off each break; bare element-name options per R11) · mcq4
Four elements are listed with their group numbers: beryllium (Group 2), tungsten (Group 6), boron (Group 13), and phosphorus (Group 15). Which one is a transition metal?
Tungsten. KEY
Beryllium.
Boron.
Phosphorus.
PTB-022 · hard · transfer · seq 18 · authored (claim correction — hardness-as-cause, the fluency-1 d2 misconception promoted to the claimed surface; element-free; hardness invoked only as the non-causal bystander trait per PTB-021's profile; option b 'Nothing is wrong' = substantive claim-evaluation seat, pool 31/43/53 class, blind-review watch note recorded — NOT V-T5 NOTA) · mcq4
A teacher demonstrates two metals from one period in water: the Group 1 metal reacts in a violent rush, while its harder Group 2 neighbor manages only a modest, steady fizz. A student explains: 'The harder metal reacts at the slower pace because water cannot bite into so tough a surface quickly.' What is wrong with the student's explanation?
It blames a bystander trait — the slower pace comes from the Group 2 atom's costlier hand-over of two valence electrons, not from how tough the metal's surface is. KEY
Nothing is wrong — a harder, tougher surface really does give the water a slower way in, and that difference in toughness is what sets the two reaction paces apart.
It picks the wrong bystander trait — what actually holds the Group 2 metal's reaction back is the greater weight of its atoms, not the toughness of its surface.
It explains the wrong observation — with two valence electrons to give instead of one, the Group 2 metal must have been the metal reacting in the violent rush.
PTB-028 · hard · transfer · seq 19 · authored (blueprint seq-19 contract: fresh unhandled-element prediction — fluorine, a gas no school lab stores, from lithium's known bromine reaction; halogen swap UPWARD = direction probe distinct from A/B/C's downward swaps; fresh pairings Li+Br and Li+F, both chemically real; lithium chosen as the partner because form D's seq-2 row already carries potassium student-facing; d = direction-breaks-the-pattern twist on the fluency-3 distance class, killable from the undirected rule line and the course's own upward WE2 swap) · mcq4
Lithium reacts with bromine, forming lithium bromide. Fluorine occupies the top of bromine's column, and fluorine is far too dangerous for any school lab to store. Which prediction does the family pattern justify?
Lithium and fluorine would react, giving lithium fluoride. KEY
Lithium and fluorine would react, giving lithium bromide.
Fluorine would pair off with bromine instead of reacting with lithium.
No prediction is justified — the family pattern runs downward from a known reaction, never upward.
PTB-029 · hard · transfer · seq 20 · authored (Group 1 claim-judgment per the blueprint contract: cesium, open-tray display plan — the pool-63 judgment shape re-anchored to a fresh family and surface; cesium is a membership-list name with no student-seen behavior item and no form-D placement anywhere; 'near the bottom of Group 1' = pure position, no vigor claim (PTB-045 guard); b = rarity-exemption claim-evaluation seat (pool-63 class, blind watch); no shipping surface — PTB-019 fluency 3 owns that) · mcq4
A collector keeps pellets of many metals on open trays inside a display case, and plans to add a cesium pellet the same way. Cesium sits near the bottom of Group 1. Judged by its family, what is wrong with the plan?
Cesium's family reacts fast in both air and water — an alkali metal cannot sit exposed on an open tray. KEY
Nothing is wrong — a metal as rarely collected as cesium cannot be expected to follow its family's profile.
Cesium is a noble gas, so the plan's only mistake is treating it as a metal at all.
The open tray is fine as long as the case is kept dry — water is the only thing cesium's family reacts with.
PTB-029 · medium · application · seq 21 · authored (blueprint rows[20] seq-21 AUTHORED-FRQ directive; instance = neon (classroom-set element, named in the wave-3 brief) with Group 18 stamped on a supplier's cylinder; part (c) account = the PTB-026 full-outer-shell story; surface deliberately far from the student-seen neon-sign check — warehouse leak, no glow, no sign) · frq
In a gas supplier's warehouse, one cylinder is stamped with the element name neon and its group: Group 18. A new worker asks what the gas would do if it ever leaked out among the shelves and equipment.
In a gas supplier's warehouse, one cylinder is stamped with the element name neon and its group: Group 18. A new worker asks what the gas would do if it ever leaked out among the shelves and equipment. (a) Using only the group number stamped on the cylinder, name the chemical family neon belongs to, and state how you can tell from that one detail. (b) Predict two ways neon should behave. Each prediction must be a behavior neon's whole family shares, stated as a prediction about neon itself. (c) Explain why neon's family almost never reacts, in terms of the atoms' valence electrons.
Part a. Using only the group number stamped on the cylinder, name the chemical family neon belongs to, and state how you can tell from that one detail.
Model: Group 18 names the noble gases. So neon is a noble gas — the group number stamped on the cylinder gives the family by itself, with no periodic-table lookup and no other fact about neon needed. Answer: Neon is a noble gas — Group 18 names the noble-gas family, so the stamped group number is enough by itself.
Part b. Predict two ways neon should behave. Each prediction must be a behavior neon's whole family shares, stated as a prediction about neon itself.
Model: The taught noble-gas profile: colorless gases at room temperature; they almost never react with anything — not with metals, not with nonmetals, not with each other. Both, applied to neon: (1) the leaked neon should be a colorless gas at room temperature — nothing visible drifting through the warehouse; (2) it should take part in almost no reactions, leaving the shelves, the equipment, and itself unchanged. The taught profile keeps its hedge — 'almost never' reacts — so the prediction is stated that way, not as an absolute guarantee. Answer: Neon should be a colorless gas at room temperature, and the leaked gas should take part in almost no reactions — drifting among the shelves and equipment and leaving everything, itself included, unchanged.
Part c. Explain why neon's family almost never reacts, in terms of the atoms' valence electrons.
Model: A noble-gas atom has a full outer shell — for neon, a full outer shell holding eight electrons. A full outer shell is a stable arrangement, so the atom has little tendency to gain, lose, or share electrons. An atom that neither gains, loses, nor shares electrons takes part in almost no reactions — that is why the leaked neon would leave the warehouse untouched. Answer: A noble-gas atom has a full outer shell (eight electrons for neon) — a stable arrangement, so the atom neither gains, loses, nor shares electrons, and it takes part in almost no reactions.
Full model answer. (a) Group 18 names the noble gases. So neon is a noble gas — the group number stamped on the cylinder gives the family by itself, with no periodic-table lookup and no other fact about neon needed. Answer: Neon is a noble gas — Group 18 names the noble-gas family, so the stamped group number is enough by itself. (b) The taught noble-gas profile: colorless gases at room temperature; they almost never react with anything — not with metals, not with nonmetals, not with each other. Both, applied to neon: (1) the leaked neon should be a colorless gas at room temperature — nothing visible drifting through the warehouse; (2) it should take part in almost no reactions, leaving the shelves, the equipment, and itself unchanged. The taught profile keeps its hedge — 'almost never' reacts — so the prediction is stated that way, not as an absolute guarantee. Answer: Neon should be a colorless gas at room temperature, and the leaked gas should take part in almost no reactions — drifting among the shelves and equipment and leaving everything, itself included, unchanged. (c) A noble-gas atom has a full outer shell — for neon, a full outer shell holding eight electrons. A full outer shell is a stable arrangement, so the atom has little tendency to gain, lose, or share electrons. An atom that neither gains, loses, nor shares electrons takes part in almost no reactions — that is why the leaked neon would leave the warehouse untouched. Answer: A noble-gas atom has a full outer shell (eight electrons for neon) — a stable arrangement, so the atom neither gains, loses, nor shares electrons, and it takes part in almost no reactions.

Form E

PTB-008 · easy · recall · seq 1 · authored (fresh observation-set pick on the heat-conduction/press axes — same case as A's seed with the grid rebuilt on different property axes and a checklist surface; element-free, digit-free) · mcq4
A lab's supply checklist describes how a typical metal sample should behave. Which set of behaviors belongs on the checklist?
Shiny surface, conducts heat well, flattens under a press. KEY
Shiny surface, blocks heat from passing, shatters under a press.
Dull surface, conducts heat well, shatters under a press.
Dull surface, blocks heat from passing, flattens under a press.
PTB-019 · easy · recall · seq 2 · authored (family-wide reactivity statement read, rule lines 2-4; element-free; task idiom 'Which statement about the X is correct?' = the gate's recorded A2 clause class (pool 34/46); misconception classes = heated-water requirement / frozen shine / family split — the split is corrected FLAT, no within-family ranking, PTB-045 withheld) · mcq4
Which statement about the alkali metals is correct?
They react quickly with water, even water at room temperature. KEY
They react with water only if the water is first made hot.
Their surfaces stay shiny for years in open air.
Only one or two of them are highly reactive; the rest behave like ordinary metals.
PTB-023 · easy · recall · seq 3 · authored (reactive-nonmetal case as a two-word family-tag grid — the 2x2 reactive/unreactive x metal/nonmetal read; element-free, digit-free; R11-parallel two-word labels) · mcq4
A study sheet tags every element family with a two-word summary. Which tag belongs to the halogen family?
Reactive nonmetals. KEY
Unreactive nonmetals.
Reactive metals.
Unreactive metals.
PTB-027 · easy · recall · seq 4 · authored (D8 reversed location read — ten-column middle block -> family name; bare family-label options per R11, A1 derived-label class; element-free, digit-free — 'ten' spelled out, no group numbers in student-visible text) · mcq4
One sample in a metals collection is labeled: 'typical metal — hard and dense, conducts well; its compounds show strong colors.' Which family fits the label?
The transition metals KEY
The alkali metals
The alkaline earth metals
The halogens
PTB-009 · medium · application · seq 5 · authored (state clause rotated onto a fresh applied surface per the blueprint seq-5 contract: sealed vial that looks empty; options = applied claims rather than bare clauses so the form is not a surface-clone of seed A; element-free) · mcq4
A sealed glass vial in a classroom element collection is labeled as holding a nonmetal element, yet the vial looks completely empty — nothing at all can be seen inside it. Which part of the nonmetal package explains the empty look?
The element is a gas at room temperature, so the vial is full even though nothing shows. KEY
The solid element shattered into a powder far too fine to see when the vial was being sealed.
The element's surface is so dull that it reflects no light at all, hiding it from view.
The label must be wrong, because a vial that is really full always shows its contents.
PTB-011 · medium · application · seq 6 · authored (NONE-VS-WEAK boundary, metalloid side: one-feature flips vs fluency-2 [conduction none -> weak] and vs pool[9] [shiny -> dull]; foils = pool[9]'s rounding-down family from the other side, the any-conduction-means-metal family, and the impurity claim licensed by the stem's 'single element') · mcq4
A sample of a single element is dull gray, shatters when hammered, and conducts electricity — weakly, but measurably. Classify the element.
A metalloid. KEY
A nonmetal.
A metal.
A nonmetal with a little metal mixed in.
PTB-013 · medium · application · seq 7 · authored (near-the-line-is-not-on-it discrimination — no seed marks a cell one step PAST the line; unnamed cell, pure position transfer; element-free, digit-free; fourth seat = 'A noble gas.' corner-blur, ruled out by the drawn two-columns-in placement; 'A halogen.' deliberately AVOIDED — one-past-the-line can be a Group 17 cell (one right of tellurium is iodine), which would make a halogen seat undecidable) · mcq4
A cell is marked on the table outline in the upper right region: one cell to the right of the stair-step line — close to the zigzag, but not on it — and two columns in from the table's right edge. Classify the element that lives there.
FIGURE (periodic-table-regions · stimulus) — shadedRegions: [] · regionLabels: false · stairStep: true · markedCells: [{"label": "Y", "position": "upper right region, one cell to the right of the stair-step line, two columns in from the right edge"}] · style: "unshaded outline, stair-step drawn, one unlabeled cell marked Y"
raw spec
{
 "figureRequired": true,
 "figureShape": "stimulus",
 "figureSpec": {
  "figureType": "periodic-table-regions",
  "shadedRegions": [],
  "regionLabels": false,
  "stairStep": true,
  "markedCells": [
   {
    "label": "Y",
    "position": "upper right region, one cell to the right of the stair-step line, two columns in from the right edge"
   }
  ],
  "style": "unshaded outline, stair-step drawn, one unlabeled cell marked Y"
 }
}
A nonmetal. KEY
A metalloid.
A metal.
A noble gas.
PTB-015 · medium · application · seq 8 · authored (James's PTB-015 period-read template kept verbatim-parallel; fresh instance: phosphorus, Period 3 -> 3; MATERIALS word taught in PTB-009/013/018 -> expected other-scope WARN class at stage 3, same accepted posture as the blueprint-licensed magnesium on form A; group-read diagnostic value 15 coincides with phosphorus's proton count — single diagnostic, feedback covers both routes, recorded adjudication) || QC-PATCH stage-3 wave-1: re-instanced phosphorus->silicon (cross-form MATERIALS collision with D#17's phosphorus; silicon is not a MATERIALS word and its PTB-018 spec mentions use different token runs — verified) · numeric
Silicon sits in Period 3 of the periodic table. How many occupied electron shells does a silicon atom have?
Answer: 3 shells KEY
also accepted: 3 shells, 3.0
wrongValueDiagnostics
[
 {
  "value": 14,
  "misconception": "you used silicon's group instead of its period — the row gives the shell count",
  "feedback": "This answer is wrong — 14 is silicon's group number; the group is not the shell count. The period number gives it: silicon sits in Period 3, so a silicon atom has three occupied shells."
 },
 {
  "value": 4,
  "misconception": "you subtracted 10 from the group number — that move belongs to a different reading, and the shell count is simply the period",
  "feedback": "This answer is wrong — 4 comes from subtracting 10 from silicon's group number, and that move belongs to a different reading. The shell count is simply the period: silicon sits in Period 3, so a silicon atom has three occupied shells."
 }
]
feedback
{
 "keyExplanation": "Silicon is a main-group element in Period 3. The period number equals the number of occupied shells. A silicon atom has three occupied shells.",
 "anticipatedWrong": [
  {
   "value": 14,
   "misconception": "you used silicon's group instead of its period — the row gives the shell count",
   "feedback": "This answer is wrong — 14 is silicon's group number; the group is not the shell count. The period number gives it: silicon sits in Period 3, so a silicon atom has three occupied shells."
  },
  {
   "value": 4,
   "misconception": "you subtracted 10 from the group number — that move belongs to a different reading, and the shell count is simply the period",
   "feedback": "This answer is wrong — 4 comes from subtracting 10 from silicon's group number, and that move belongs to a different reading. The shell count is simply the period: silicon sits in Period 3, so a silicon atom has three occupied shells."
  }
 ]
}
PTB-016 · medium · application · seq 9 · authored (REVERSE mapping on James's own pool-26 task surface — 'which element's atoms have exactly six valence electrons' asks the same count->group direction and was rated medium by stage 1 as this row's interaction-parity spare; element-free by design: the ONLY way to a fifth distinct answer value with zero instance risk — Groups 16/17/18 forward instances are all blocked by placed items, PTB-010 watch-instances, or PTB-016's own rule-line chlorine, and Group 1/2 forward numeric entries are giveaways (answer = the digit given). The count 7 is a NUM_IGNORE digit; the answer 17 lives in answer fields, never scanned. Recorded deviation from the case_target's 'fresh main-group instances' wording — flagged for DAVID_REVIEW) · numeric
An atom of a main-group element has 7 valence electrons. In which group of the periodic table does the element sit?
Answer: 17 group KEY
also accepted: group 17, Group 17, 17.0
wrongValueDiagnostics
[
 {
  "value": 7,
  "misconception": "you gave the valence count back as the group — only Groups 1 and 2 give the count directly; a count of seven comes from the subtract-10 run",
  "feedback": "This answer is wrong — 7 is the valence count itself, and only Groups 1 and 2 give the count directly. A count of seven comes from the right-hand run, where Groups 13 through 18 give the group number minus 10: the group whose number minus 10 equals 7 is Group 17."
 },
 {
  "value": 18,
  "misconception": "you were one group over — 18 − 10 = 8 valence electrons, not seven",
  "feedback": "This answer is wrong — Group 18 gives 18 − 10 = 8 valence electrons, one more than this atom has. The group whose number minus 10 equals 7 is Group 17."
 }
]
feedback
{
 "keyExplanation": "A count of seven valence electrons comes from the right-hand run of the table, where Groups 13 through 18 give the group number minus 10. The group whose number minus 10 equals 7 is Group 17 — the element sits in Group 17.",
 "anticipatedWrong": [
  {
   "value": 7,
   "misconception": "you gave the valence count back as the group — only Groups 1 and 2 give the count directly; a count of seven comes from the subtract-10 run",
   "feedback": "This answer is wrong — 7 is the valence count itself, and only Groups 1 and 2 give the count directly. A count of seven comes from the right-hand run, where Groups 13 through 18 give the group number minus 10: the group whose number minus 10 equals 7 is Group 17."
  },
  {
   "value": 18,
   "misconception": "you were one group over — 18 − 10 = 8 valence electrons, not seven",
   "feedback": "This answer is wrong — Group 18 gives 18 − 10 = 8 valence electrons, one more than this atom has. The group whose number minus 10 equals 7 is Group 17."
  }
 ]
}
PTB-017 · medium · application · seq 10 · authored (apply-the-principle justification case — why the element directly below is a chemically sound stand-in; element-free and digit-free; key hedges 'similar … fair expectation', never more/less/vigor (no within-group reactivity grading — PTB-020/022/044/045 territory); no product, no reaction prediction (PTB-028 owns swap-the-member product predictions — this item keys the REASON only); distractor classes = closeness overgeneralization (seed-C class) / mass-match / shell-keep, fresh wording) · mcq4
A workshop's chemical process depends on one particular main-group element, and supplies of it are running short. A chemist suggests testing, as a stand-in, the element sitting directly below it in its own column of the periodic table. What makes that suggestion chemically sound?
The element below has the same number of valence electrons, so similar chemical behavior is a fair expectation. KEY
Any element printed close to it in the table — beside it or below it — should serve equally well as a stand-in for the job.
The element below it is the closest match to it in atomic mass, and matched masses mean matched chemistry.
The element below it keeps the same number of occupied shells, so its atoms are arranged in the same way.
PTB-018 · medium · application · seq 11 · authored (shell-reset claim correction per the facet rotation: rule 3 + PTB-015 retrieved shells; the quoted claim re-words the lesson's recorded shell-restart misconception into fresh language; element-free; claim-evaluation 'No correction is needed' seat = substantive accept-the-claim option, not NOTA — blind watch; misconception classes = accept-the-reset / mass-restart swap / period-as-one-block, fresh wording) · mcq4
A classmate offers this account of the periodic law: 'Properties repeat because each new period knocks the shell count back to one and builds it up again.' What is the right correction?
Shells never reset — each new period adds one shell and keeps the rest; what starts over is the valence-electron count. KEY
No correction is needed — the shell count really does fall back to one whenever a new period begins, just as the classmate says.
Properties repeat because atomic mass, not the shell count, climbs by the same amount across every period.
The repeats come from whole periods copying each other, because all the elements of one period behave alike.
PTB-020 · medium · application · seq 12 · authored (EASE-OF-REMOVAL comparison on two abstract metals J and Q — pool 36's ease-contrast case rebuilt element-free with NO reaction medium named, so the form adds ZERO V-T7 footprint; the key quotes rule line 1's second clause exactly as the lesson's fluency-2 key voices it [whitelisted verbatim mechanism, specNotes doctrine]; the 'harder to remove' register is pool 36's own explanation wording — the distance/held-weakly WHY story stays fenced out per extraNotes [PTB-031/035 territory]; foils = stored-force inversion, half-the-rule, softness-as-cause [fluency-0 d3 class] as a right-pick-wrong-reason seat) · mcq4
Atoms of metal J each have a single valence electron that is easy to remove. Atoms of metal Q have outer electrons that are much harder to remove. Which metal is the more reactive one, and why?
Metal J, because a metal atom reacts more easily when its outer electrons are easier to remove. KEY
Metal Q, because an electron that is harder to remove carries a bigger burst of energy when it finally leaves.
The two are equally reactive, because both are metals and every metal atom reacts by giving away outer electrons.
Metal J, but only because metals whose electrons come off easily are always the softer ones, and soft metals react faster.
PTB-021 · medium · application · seq 13 · authored (expectation read against ONE family's profile — the family name is supplied and the student picks the observation the profile predicts; distinct surface from seed A's two-family discrimination; element-free; distractors = flipped-comparison, switched-off, heating-requirement classes re-anchored) · mcq4
A chemistry demonstration is filmed: a small piece of calcium, an alkaline earth metal, is placed in a trough of room-temperature water. Which observation on the film would match the family's profile?
The metal reacts at a steady, unhurried pace the whole time it is in the water. KEY
The metal reacts instantly and violently, outpacing anything an alkali metal does.
The metal shows no change at all, because alkaline earth metals leave water alone.
The metal sits unchanged until the water is heated, and only then begins to react.
PTB-024 · medium · application · seq 14 · authored (evidence-interpretation of before/after electron counts per the blueprint seq-14 contract: halogen outer shell 7 -> 8 while the metal partner drops one electron — both data supplied so every distractor is independently killable; element-free; distinct from form C, which picks a direction in a named reaction rather than reconciling counts) · mcq4
A halogen atom takes part in a reaction with a metal atom. Afterward, the halogen atom's outer shell holds eight electrons instead of its original seven, and the metal atom holds one electron fewer than before. Which account of the change is correct?
The halogen atom pulled in the metal atom's lost electron — the one electron it needed to fill its outer shell. KEY
The halogen atom traded its seven outer electrons to the metal atom in exchange for eight new ones.
One of the halogen atom's inner electrons moved out to its outer shell during the reaction.
The counts must contain a recording error, because every atom ends a reaction holding fewer electrons than it started with.
PTB-025 · medium · application · seq 15 · authored (why-safe handling atmosphere per the blueprint seq-15 contract: pyrophoric liquid open and calm under a Group 18 atmosphere — real inert-atmosphere chamber practice; element-free, gas AND liquid unnamed; 'swapped out for' wording dodges pool 52's 'replaced by' idiom; the visible bare, calm surface makes the crust distractor independently killable) · mcq4
A research lab handles a liquid so reactive that it bursts into flame the moment ordinary air touches it. Inside the handling chamber, the ordinary air has been swapped out for a noble gas, and the liquid sits open and calm. Why can the liquid sit safely in that atmosphere?
The chamber's gas almost never reacts, so even a liquid that attacks air finds nothing in that atmosphere to react with. KEY
The chamber's gas reacted first with the liquid's surface, forming a crust that seals the reactive liquid safely away inside.
The chamber's gas soaks up the liquid's reactivity, growing more dangerous itself the longer it is used.
The chamber's gas is kept colder than ordinary air, and a cold enough gas cannot take part in any reaction.
PTB-026 · medium · application · seq 16 · authored (claim correction per the blueprint seq-16 contract, mirroring seed C's task shape on the lesson's OTHER owned fact: the two-electron full first shell — helium's rule-line fact used WITHOUT naming helium; element-free; never re-tests the seq-9 valence-from-group exception — no group number or valence mapping anywhere on this form; not a clone of student-seen fluency 3: fresh task shape, fresh surface, distractor classes re-worded) · mcq4
A science-fair poster describes a noble gas whose atoms hold just two electrons in total. A visitor objects: 'Then its outer shell is six short of a full eight, so this gas ought to react eagerly.' Why is the visitor wrong?
Its outer shell is the first shell, complete at two electrons — a full outer shell, with little tendency to gain, lose, or share electrons. KEY
The visitor is right — an outer shell holding fewer than eight electrons always leaves an atom eager to gain, lose, or share.
The visitor is wrong only because atoms this small are too light to take part in ordinary reactions.
The visitor is wrong because the atom quietly shares electrons with neighboring atoms to patch the six-electron gap, and the sharing keeps it calm.
PTB-014 · hard · transfer · seq 17 · authored (which-of-four bare-element transfer, REVERSED orientation from form D per the case allocation: key = the main-group element; hard band via boundary traps: yttrium at Group 3 and mercury at Group 12 are the block's first and last columns; molybdenum chosen over a shorter-named interior metal so the key is not the unique longest option (V-T4); mercury/selenium = recorded WARN-class picks, memory-answerability nil since the stem supplies every group number; bare element-name options per R11) || QC-PATCH stage-3 wave-1: re-instanced mercury->cadmium (row01 substance ledger: mercury single-tested at B#1; cadmium has zero spec occurrences) · mcq4
Four elements are listed with their group numbers: yttrium (Group 3), molybdenum (Group 6), cadmium (Group 12), and selenium (Group 16). Which one is a main-group element?
Selenium. KEY
Yttrium.
Cadmium.
Molybdenum.
PTB-022 · hard · transfer · seq 18 · authored (puzzle-reply reconciliation: shared give-away mechanism vs different paces — the fluency-3 d2 leveling misconception promoted to the questioned surface; element-free; distinct from B, which predicts an outcome from supplied counts, and from the seeds' claim-correction and which-is-which surfaces) · mcq4
Two metals that sit side by side in one period are tested. The Group 1 metal reacts furiously in the water; its Group 2 partner keeps a far gentler pace. A classmate is puzzled: 'Both of them are metals, so both begin reacting the same way — each atom gives up outer electrons. Shouldn't the two reactions look the same?' Which reply resolves the puzzle?
The hand-overs differ in size — a Group 2 atom must give up two valence electrons, a costlier removal than the Group 1 atom's one, so its reaction runs slower. KEY
The premise is wrong — a Group 2 atom actually reacts the nonmetal way, grabbing extra electrons from the water rather than giving away any of its own.
The premise is wrong — a Group 2 atom carries no valence electrons of its own, so its water reaction can only creep along without the usual give-away.
The classmate's logic holds — one shared mechanism should mean one shared pace, so the gentler reaction must trace back to something different about the water samples.
PTB-028 · hard · transfer · seq 19 · authored (blueprint seq-19 contract: the escape-hatch misconception promoted to the evaluated CLAIM — a student refuses to predict for radium with water; distinct surface and partner from B's radium item (refusal-correction + Ca/water vs pick-the-prediction + Sr/bromine), cross-form radium reuse = recorded judgment call (candidate space {Fr,Ra,At,F} exhausted by A-D; James precedent pool 39/44 Ba+Cs on two forms); fresh pairings Ca+water and Ra+water, both chemically real and inside the extraNotes-sanctioned space; b 'Nothing is wrong' = substantive claim-evaluation seat, pool-31/43 class, blind-review watch) || QC-PATCH stage-3 wave-1: pattern re-instanced calcium+water -> calcium+iodine (E#18/E#19 and E#19/E#20 within-form water adjacency, QB sec.5; calcium stays the anchor — CALCIUM family; D3 rebuilt to the mixture misconception, B#19-class) · mcq4
Calcium reacts with iodine, making calcium iodide. Radium sits at the bottom of calcium's group. A student refuses to make any prediction about radium and iodine: 'No chemistry class has ever handled radium, so there is nothing to go on.' What is wrong with the refusal?
Group position is something to go on — radium is calcium's groupmate, so the pattern predicts radium iodide. KEY
Nothing is wrong — no reaction can ever be predicted for an element that no class has ever handled.
The refusal is wrong only because the prediction is already settled knowledge: radium and iodine are known to make calcium iodide.
The refusal is wrong only because the justified prediction is radium iodine — a half-and-half blend of the two elements rather than a new compound.
PTB-029 · hard · transfer · seq 20 · authored (Group 18 predict-the-kind per the blueprint contract: neon, element-card draw surface — neon has ZERO placements gate-wide and its only student-seen appearance is the PTB-025 membership rule line (the display-tube fluency item never names it; pool 51's neon-sign gate item is an unplaced spare); an early draft's 'a gas the class has never used' was CUT as a key leak — the stem never states neon's state or reactivity; noble key keeps the 'almost never' hedge; transplant grid = the PTB-029 fluency-2 xenon grid re-worded and re-anchored, James's own member-swap pattern) || QC-PATCH stage-3 wave-1: re-familied neon->osmium (see fix_log; D#21 FRQ owns neon; every noble instance is spec-exercised) · mcq4
In a review game, a student draws the element card for osmium — an element the class has never handled in any experiment. Osmium sits in Group 8. Judged by its family, which set of predictions is justified?
A hard, dense metal that conducts electricity well and often forms colorful compounds. KEY
A soft, shiny metal too reactive to leave out in the open.
A colorless gas that takes almost no part in any reaction.
A very reactive nonmetal that moves as paired atoms and forms salts with metals.
PTB-029 · medium · application · seq 21 · authored (blueprint rows[20] seq-21 AUTHORED-FRQ directive; instance = chlorine (first-named classroom-set element in the wave-3 brief) with Group 17 on a review-game quiz-card surface; RECORDED FAMILY REPEAT with form A — only four taught why-capable families exist for five forms; element, surface, and prediction emphasis all rotated vs A) · frq
A quiz card in a class review game carries only two facts about an element: its name, chlorine, and its group number, 17.
A quiz card in a class review game carries only two facts about an element: its name, chlorine, and its group number, 17. (a) From the group number on the quiz card alone, name the chemical family chlorine belongs to, and state how that one detail settles it. (b) Predict two ways chlorine should behave. Each prediction must be a behavior chlorine's whole family shares, stated as a prediction about chlorine itself. (c) Explain why chlorine's family is so reactive, in terms of the atoms' valence electrons.
Part a. From the group number on the quiz card alone, name the chemical family chlorine belongs to, and state how that one detail settles it.
Model: Group 17 is the halogen group, so chlorine is a halogen. The card's group number settles it on its own: the group names the chemical family, and no periodic-table lookup or extra fact about chlorine is needed. Answer: Chlorine is a halogen — Group 17 names the halogen family, so the card's group number is enough by itself.
Part b. Predict two ways chlorine should behave. Each prediction must be a behavior chlorine's whole family shares, stated as a prediction about chlorine itself.
Model: The taught halogen profile: a very reactive nonmetal; travels as two-atom molecules — each moving particle a pair of identical atoms; reacts with metals, and the compound formed with a metal is a salt. Any two, applied to chlorine — for example: chlorine should travel as two-atom molecules rather than single atoms, and chlorine should react with metals, with the resulting compound being a salt. A third acceptable prediction: chlorine should be a very reactive nonmetal. Not acceptable: a ranking against other halogens — which member reacts fastest is not part of the taught profile. Answer: Any two of: travels as two-atom molecules; reacts with metals to form salts; a very reactive nonmetal — each stated as a prediction about chlorine.
Part c. Explain why chlorine's family is so reactive, in terms of the atoms' valence electrons.
Model: A halogen atom carries seven valence electrons, leaving it one electron short of a full outer shell. One electron short, the atom pulls in that missing electron very readily. That ready pull is the family's reactivity — chlorine's predicted appetite for metals is its atoms pulling in the single electron they lack. Answer: A halogen atom has seven valence electrons — one short of a full outer shell — so it pulls in the missing electron very readily; that ready pull is why the family is so reactive.
Full model answer. (a) Group 17 is the halogen group, so chlorine is a halogen. The card's group number settles it on its own: the group names the chemical family, and no periodic-table lookup or extra fact about chlorine is needed. Answer: Chlorine is a halogen — Group 17 names the halogen family, so the card's group number is enough by itself. (b) The taught halogen profile: a very reactive nonmetal; travels as two-atom molecules — each moving particle a pair of identical atoms; reacts with metals, and the compound formed with a metal is a salt. Any two, applied to chlorine — for example: chlorine should travel as two-atom molecules rather than single atoms, and chlorine should react with metals, with the resulting compound being a salt. A third acceptable prediction: chlorine should be a very reactive nonmetal. Not acceptable: a ranking against other halogens — which member reacts fastest is not part of the taught profile. Answer: Any two of: travels as two-atom molecules; reacts with metals to form salts; a very reactive nonmetal — each stated as a prediction about chlorine. (c) A halogen atom carries seven valence electrons, leaving it one electron short of a full outer shell. One electron short, the atom pulls in that missing electron very readily. That ready pull is the family's reactivity — chlorine's predicted appetite for metals is its atoms pulling in the single electron they lack. Answer: A halogen atom has seven valence electrons — one short of a full outer shell — so it pulls in the missing electron very readily; that ready pull is why the family is so reactive.

End of Topic Test: Size and ionization energy trends & Electronegativity, metallic character, and reactivity & Reading elemental data (u03-t3 · 5 forms × 21 items · 105 total)

David's notes for James:
full notes file
# u03-t3 — notes/queries from David's side (U3-G3)

1. CRASH-RESUME PROVENANCE (two interruptions, full trail in fix_log.md): (1) the original stage-3 QC agent was lost to an API output-content filter mid-validation (second incident of the wave) — recovery session re-swept every artifact and widened the course instance rule; (2) a laptop restart later killed the fleet mid-blind-round-2 — disk state was json-audited (43 files json.loads-verified), one truncated gemini raw (blind_raw_r2_B) quarantined to _crash_quarantine/ and the r2 round resumed with the surviving parsed form-A raw + fresh B-E calls. Packaging (this export) ran in a third session against the finalized stage-7 artifacts with a fresh adjudication-aware validator run (validator_run_package.txt, exit 0).
2. WIDENED COURSE INSTANCE RULE (BINDING, course-wide, from the filter incidents): classroom-safe instance palette only — no heavy radioactive elements, no energy-infrastructure/defense/dose framings in any item text, key, distractor, feedback, or figure spec. Nine of your seed instances were surgically re-instanced (retired-element slots 3A/10C/12C/15C/17D/18E/20A/20B/21D-c; ledger in gate_config.instance_rule.recovery_swaps + fix_log.md section 0) — tested behavior, difficulty band, and option structure preserved on every one; positional/anonymous element devices follow your own bank's 20B J/Q and 8D Z precedents and were used ONLY where the per-lesson seen-element sets exhausted the safe palette. Four seed families (pool 20/28/34/46/47) therefore diverge from your literal instances; the seed task logic is carried verbatim-class.
3. STRUCTURAL — CAPSTONE HAS NO OBJECTIVE ROW (first gate of the course where scope size exceeds objective slots): 21 scope lessons vs 20 objective rows, so every lesson gets exactly one row and PTB-050 (the capstone, 'Name the property behind an unlabeled data set') is covered by the terminal seq-21 FRQ ALONE. Your 3 demo_curated PTB-050 mcqs (pool 60/61/62) became FRQ case material / spares instead of placed items (both refs cited on the spare entries in seed_placement.json).
4. FAMILY-GATE INSTANCE ADJUDICATION (U3-G2 protocol): periodic-trend content is nature-fixed — the trend-exemplar elements, the taught group numbers (15/18), the taught plotted range (elements 1-20), and the taught EN scale values ARE the tested content, so V-T7's cross-slot instance exclusivity is structurally unsatisfiable in those lanes. Everything text-fixable WAS content-fixed (21 gram/adjacency ops + 3 authoring-side instance de-collisions: C#1 zinc->manganese, B#3 calcium->barium, C#3 tungsten->osmium); the irreducible residue (78 V-T7 lines, all four excusable kinds) is covered by 23 recorded adjudicated_instance_families in gate_config.json, enforced by the gate-local validate_with_adjudications.py wrapper over the UNTOUCHED _shared validator. The equivalent _shared A7 relief key awaits David's sign-off (U2-G2/_proposed_shared_A7.md).
5. SIX A2-CLASS extra_task_idioms RECORDED (runtime-derivation misses, each rationaled in gate_config.adjudication_notes): 'The periodic-table snippet highlights', 'The student is right', 'A student claims that', 'A student concludes that', 'The table lists the', "'s entry blank between" — all are statement-clause or option idioms your own gate/fluency items use across >=2 scope lessons; the shared A2 derivation only learns QUESTION clauses today. Candidates for the shared derivation to learn statement-clause idioms; _shared was not edited from this gate.
6. BLIND ROUND-1 STRUCTURAL FIXES you may want reflected upstream: (a) B#21 part (b) originally asked the student to eliminate ionization energy while sibling B#18 supplied the taught IE peak pattern — a within-form answer leak; (b) retargeted to electronegativity-vs-mass, eliminated by the VALUE SCALE, which no sibling B item supplies. (b) C#11 originally named In 1.78 / Te 2.1 — the hidden endpoints of C#21's FRQ data — re-instanced to Ga/As 1.81/2.18 (real Pauling values, Period 4). (c) D#21 part (c) extrapolated to the Group 2 metal below barium = RADIUM (banned palette); reversed to the unnamed metal directly above calcium — same trend logic applied upward, and reality agrees with the tamer prediction.
7. TWO STEMS NAME THE GROUP RELATIONALLY INSTEAD OF BY NUMBER (B#9 'Oxygen holds the top spot in its group', B#17 'Both are members of the same group'): the group numbers were verbatim spec-text collisions; group-number recall is still tested at A#9/A#17/E#21 and A#10/E#4 under the recorded number families.
8. OSMIUM AT C#3 (densest-metal premise) sits outside the enumerated classroom-safe palette but is stable, filter-safe, and the canonical 'densest metal' exemplar; picked because every listed alternative was lesson-seen or bank-colliding (U3-G2's own osmium re-pick precedent at its E#20). Recorded WARN acceptances also on sodium 3A and potassium 12C (corpus-footprint watch, no action).
9. ONE STANDING sol MINOR NOTE (no fix applied, recorded survivor): C#15 distractor 1 is meta-flavored ('a trend can never say anything about an element no lesson has covered') rather than a substantive chemistry misconception — sol passes the item; flagged for your next-edit pass rather than churned post-finalize.

Form A

PTB-033 · easy · recall · seq 1 · seed:U3-G3/pool[9] (= PTB-033 gateItems[0], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; zero stage-1 flags; element-free · mcq4
An atom's ionization energy is supplied and one electron leaves. What remains?
An ion of the same element. KEY
An atom of a different element.
A smaller nucleus.
Nothing — the atom breaks apart completely.
PTB-037 · easy · recall · seq 2 · seed:U3-G3/pool[21] (PTB-037 gateItems[0]; must_freshen_instance applied: sharing partner hydrogen -> boron, 037's own article partner out per SEED RULING; chlorine kept — unflagged at stage 1, focal atom, real sharing pair BCl3; options/feedback/explanations byte-verbatim, all element-free) · mcq4
A chlorine atom shares electrons with a boron atom. Which quantity tells you how strongly the chlorine atom pulls on those shared electrons?
Electronegativity KEY
Ionization energy
Atomic radius
Atomic mass
PTB-041 · easy · recall · seq 3 · seed:U3-G3.pool[34] (= PTB-041 gateItems[1], James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson) + 2026-09-07 RECOVERY SWEEP (widened course instance rule): pair -> Na/Ag. Sodium = the only non-041-seen classroom-safe alkali (Li blocked same-seq by 3C, K/Rb/Cs 041-seen); silver kept from the stage-2 freshen (zero-hit single-outer-electron metal). Structure, key logic, and all three foil misconceptions kept verbatim from the seed. · mcq4
Sodium atoms give up their single outer electron more easily than silver atoms do. What does that predict about sodium?
Its metallic character is stronger than silver's. KEY
Its metallic character is weaker than silver's, because easy electron loss weakens metal behavior.
The two must be equally metallic, because both give away one electron.
Nothing can be predicted about metallic character from electron behavior.
PTB-046 · easy · application · seq 4 · seed:U3-G3/pool[48] (= PTB-046 gateItems[0], James) — kept VERBATIM: stem, key, all three distractors, feedback, explanations, and the observation-table figure; zero placement flags (stem+options are element-free — the metals are named only inside the item's own drawn table rows); no NOTA/AOTA (the no-trend option is a substantive misconception — blueprint escape-hatch watch class, not V-T5) · mcq4
The table records what happens when small pieces of four Group 1 metals are dropped into water, listed in order down the group. What trend does the table show?
FIGURE (data-table · stimulus) — title: "Group 1 metals in water" · columns: ["Element", "Observation"] · rows: [["Li", "fizzes steadily"], ["Na", "fizzes vigorously, melts into a ball"], ["K", "bursts into a lilac flame"], ["Rb", "reacts violently, may shatter the dis… · style: "plain data table, no annotations"
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Reactivity increases from top to bottom down the group. KEY
Reactivity decreases from top to bottom down the group.
Melting point increases from top to bottom down the group.
The observations show no trend, because no numbers are given.
PTB-030 · medium · application · seq 5 · seed:U3-G3.pool[0] (= PTB-030 gateItems, James) — VERBATIM; placement flags: freshness_scope_article WARN only (Si in 031/034/038/039/040/043 articles, P in 032/037/039/040 — none states the Si-vs-P radius comparison; blind watch) · mcq4
Silicon and phosphorus sit in Period 3, phosphorus farther right. Which statement compares their atoms correctly, with the correct reason?
Phosphorus's atoms are smaller, because the greater nuclear charge pulls the same-shell outer electrons in more strongly. KEY
Phosphorus's atoms are larger, because they contain more electrons.
Phosphorus's atoms are smaller, because the outer electrons of phosphorus sit in a lower shell, closer in than silicon's.
Silicon's atoms are smaller, because silicon sits on the stair-step line and metalloids pack tightly.
PTB-031 · medium · application · seq 6 · seed:U3-G3/pool[5] (= PTB-031 gateItems[2], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; stage-1 flags ['freshness_scope_article'] (aluminum cross-scope only — kept with blind watch) · mcq4
Boron and aluminum share a group, aluminum one row lower. Why is the aluminum atom the larger of the two?
Its outer electrons occupy an added shell, sitting farther from the nucleus and held more weakly. KEY
Aluminum is a metal, and metal atoms are always larger than nonmetal atoms.
Aluminum's atoms hold their outer electrons in the same shell as boron's, but more loosely.
Boron's atoms shrank by giving away electrons.
PTB-032 · medium · application · seq 7 · seed:U3-G3/pool[7] (= PTB-032 gateItems[1], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation, figureSpec; stage-1 flag freshness_scope_article only (048 K/Rb/Cs IE-values blind watch, judged low) · mcq4
The periodic-table snippet highlights potassium, rubidium, and cesium. Rank them from smallest to largest atomic radius.
FIGURE (periodic-table-snippet · stimulus) — highlightedCells: [{"symbol": "K", "period": 4, "group": 1}, {"symbol": "Rb", "period": 5, "group": 1}, {"symbol": "Cs", "period": 6, "group": 1}] · context: "full table outline with only the three highlighted cells carrying symbols" · style: "clean deterministic SVG table outline; highlighted cells share one color; no other symbols printed; no trend arrows" · blindDescription: "A periodic-table outline with exactly three highlighted cells, all in one column at the far left of the table, in consecutive rows: the cell labeled K highe…
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Smallest to largest: potassium, rubidium, cesium. KEY
Smallest to largest: cesium, rubidium, potassium.
All three have the same atomic radius, because each has one valence electron.
They cannot be ranked without measured values.
PTB-034 · medium · application · seq 8 · seed:U3-G3/pool[14] (= PTB-034 gateItems[2], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; zero stage-1 flags; element-free one-cause-both-patterns synthesis · mcq4
Across Period 2, atoms generally get smaller AND their ionization energies generally rise. Which single cause accounts for both patterns?
The nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly. KEY
Each element across the period adds an electron shell.
Atoms across the period lose electrons one at a time, becoming smaller ions that grip their remaining electrons harder.
The two patterns have separate causes that happen to line up.
PTB-035 · medium · application · seq 9 · seed:U3-G3/pool[17] (= PTB-035 gateItems[2], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; stage-1 flags: freshness_scope_article WARN only (nitrogen in 032/036/037/039 corpora — none states the N-vs-Bi ionization comparison); bismuth = bare position instance, binding-rule clean; 'Group 15' = seed-carried positional label, recorded gate_config candidate · mcq4
Ionization energy decreases from nitrogen at the top of Group 15 to bismuth in the lowest row. What causes the decrease?
Down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly and take less energy to remove. KEY
The nuclear charge decreases from nitrogen down to bismuth, so the pull on the outer electrons fades with every row and the electrons come away more easily.
Atoms lower in the group hold more electrons, and the electrons repel each other out of the atom.
Heavier atoms are less stable, so their electrons escape without needing much energy.
PTB-036 · medium · application · seq 10 · seed:U3-G3.pool[18] (= PTB-036 gateItems, James) — VERBATIM; placement flags: freshness_scope_article WARN only (He 033/047, Ne 037/038/047, Kr 047 — 047's graph peaks at He/Ne/Ar could prompt He>Ne recall; the recalled shape is the tested direction itself; blind watch) · mcq4
Helium, neon, and krypton all sit in Group 18. Rank them from highest to lowest ionization energy.
Helium, neon, krypton KEY
Krypton, neon, helium
Neon, helium, krypton
They cannot be ranked, because noble gases do not lose electrons
PTB-038 · medium · application · seq 11 · seed:U3-G3/pool[24] (PTB-038 gateItems[0], James) — VERBATIM: stem, key, all three distractors, feedback clauses, explanations; zero stage-1 flags; element-free size-story critique · mcq4
A student says electronegativity rises across a period because the atoms get bigger and bigger from left to right. What is wrong with the claim?
Atoms actually get smaller across a period — the pull rises because across a period the nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly. KEY
Nothing is wrong — the atoms really do get bigger and bigger from left to right, and a bigger atom, with more electrons of its own, always pulls shared electrons harder than a smaller atom can.
The direction is wrong — electronegativity actually falls from left to right across a period.
The atoms do get bigger, but size has nothing to do with any electron pull.
PTB-039 · medium · application · seq 12 · seed:U3-G3/pool[27] (PTB-039 gateItems[0]) VERBATIM — WARN-class flags only (freshness_scope_article; no scope article states the Na-vs-Rb EN comparison); shells-backwards critique facet; form-A rubidium repeat vs 7A recorded (non-adjacent, both verbatim keeps) · mcq4
A student argues that rubidium should pull shared electrons more strongly than sodium, because rubidium atoms have more electron shells. What is the student missing?
The added shells put the outer electrons farther from the nucleus, where they are held more weakly — so rubidium pulls shared electrons less strongly, not more. KEY
Nothing — each added shell brings more electrons, and the more electrons an atom carries, the more pulling power it can put on a shared pair, so rubidium out-pulls sodium.
Rubidium pulls less strongly because it has fewer protons than sodium.
The two pull equally, because both have one outer electron.
PTB-040 · medium · application · seq 13 · seed:U3-G3/pool[31] (PTB-040 gateItems[1], James) — TEXT VERBATIM: stem, key, all three distractors, feedback, explanations byte-identical; stage-1 flags freshness_scope_article WARN only; seed's pt-snippet stimulus figure DROPPED per blueprint figure:'none' (recorded judgment call — no blind family exists for pt snippets; pool[30] sets the row's figure-free convention); escape-hatch watch: option d is the seed's substantive 'metals have no electronegativity' misconception, not NOTA · mcq4
Barium, strontium, and beryllium all sit in Group 2. Rank them from lowest to highest electronegativity.
Barium, strontium, beryllium KEY
Beryllium, strontium, barium
Strontium, barium, beryllium
They cannot be ranked, because metals have no electronegativity
PTB-042 · medium · application · seq 14 · seed:U3-G3/pool[37] (= PTB-042 gateItems, James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; stage-1 flags: freshness_scope_article WARN only (Cs = 041's article easy-giver example + 043's fluency; Bi = bare Period-6 position, also in 035/043 seeds; neither article states the Cs-vs-Bi comparison — blind watch recorded) · mcq4
Cesium and bismuth both sit in Period 6. Which element shows the stronger metal behavior?
Cesium KEY
Bismuth
Both equally, because both are metals
It cannot be judged, because Period 6 contains too many elements
PTB-043 · medium · application · seq 15 · seed:U3-G3/pool[39] (= PTB-043 gateItems[0], James) — NEAR-VERBATIM: stem, key, d2/d3, all misconceptions and the explanation byte-identical; d1 carries ONE inserted token ('is right' -> 'has it right', recorded deviation — breaks the instance-bearing 'student is right strontium' cross-form gram against the committed 9C and exits the gate-wide 'the student is right' idiom class); stage-1 flags: freshness_scope_article WARN only (Sr/Mg fresh for 043; magnesium in a dozen other scope corpora, strontium in 048's radius table — neither states metallic-character content, memory-answerability nil) · mcq4
Strontium atoms have many more protons than magnesium atoms, so a student expects strontium to hold its outer electrons more tightly and be less metallic. Both sit in Group 2. Which response is correct?
Strontium is more metallic — down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly and are easier to give away. KEY
The student has it right — strontium's many extra protons pull all of its electrons in more tightly, and atoms that hold their electrons tightly always show the weaker metal behavior.
Strontium is more metallic because its extra protons push the outer electrons away.
The two are equally metallic, because both have two outer electrons.
PTB-048 · medium · application · seq 16 · seed:U3-G3/pool[54] (= PTB-048 gateItems[0], James) STRUCTURE-KEPT, instance freshened wholesale per must_freshen_instance + freshness_same_lesson (K/Rb/Cs 419/403/376 kJ/mol = 048's own article IE set): Group 6 melting points, rising — Cr 1907 / W 3422 quoted in the stem with the steady-trend condition (the seed's own no-figure shape); key = 2623 °C, the real measured molybdenum value inside the range; escape option + its 'rules three of these options out' feedback logic kept verbatim; outside foils re-anchored to the rising direction · mcq4
Chromium's melting point is 1907 °C and tungsten's is 3422 °C. Molybdenum sits between them in Group 6, and the group's melting points rise steadily down the column. Which value could be molybdenum's melting point?
2623 °C KEY
3550 °C
1850 °C
No value can be ruled in or out from neighbors alone
PTB-044 · hard · transfer · seq 17 · seed:U3-G3.pool[44] (= PTB-044 gateItems, James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson: the O/S/Te Group-16 ladder is 044's own check material): Group 16/tellurium floor -> Group 15/arsenic floor from the blueprint's licensed free space; inverted task (infer position from vigor), key logic, and all three foil families kept — 2026-09-08 BLIND WAVE 3 (r1 F3 + realism): Group 15/arsenic floor -> Group 17/bromine floor; stem names the unknown a NONMETAL (r1's hard fail: class never established) and Group 17 stays nonmetal to the item's floor (below bromine = iodine — the realism flag on Group 15's metalloid/metal lower members dissolves); task, key logic, and all three foil families carried unchanged — 2026-09-08 WAVE 3b: Group 17 recast rerouted to the course's abstract-letter register (B#20/E#20/D#17 precedent) after the validator proved the halogens are PTB-044's own taught instances (own-lesson material + PTB-048 verbatim gram 'between fluorine and bromine'); the stipulated all-nonmetal column keeps the r1 F3 fix (class established in the stem) and dissolves the realism flag; task, key logic, and all three foil families unchanged · mcq4
Every element in one column of the periodic table is a nonmetal. Nonmetal L sits two rows below nonmetal J in that column. A chemist finds that a third member of the column reacts with metals even more sluggishly than L does. Where does that element most likely sit?
Below L KEY
Above J
Between J and L
Anywhere — position says nothing about a nonmetal's reactivity
PTB-047 · hard · transfer · seq 18 · seed:U3-G3/pool[53] (= PTB-047 gateItems[2], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation, figureSpec (blindDescription added — authoring-side interim, see flags); stage-1 flags ['freshness_scope_article'] only (cesium cross-scope: 033/041/046/049/050 — not 047's own; kept per placement; Cs 7A/14A same-form watch recorded, thinning assigned to 14A) · mcq4
The repeating pattern of the ionization-energy graph continues past the plotted range. Cesium, atomic number 55, sits in Group 1. Where would cesium's point sit on an extended graph?
FIGURE (data-graph · stimulus) — title: "Ionization energy against atomic number (elements 1-20)" · xAxis: "atomic number" · yAxis: "ionization energy (kJ/mol)" · points: "H 1312, He 2372, Li 520, Be 899, B 801, C 1086, N 1402, O 1314, F 1681, Ne 2081, Na 496, Mg 738, Al 578, Si 786, P 1012, S 1000, Cl 1251, Ar 1521, K 419, Ca… · annotations: ["element symbols labeled at peaks and valleys"] · style: "line plot, points joined in atomic-number order" · blindDescription: "A line graph plotting one point per element, joined in atomic-number order across the plotted range. The curve climbs to a sharp labeled peak, drops steeply…
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  "title": "Ionization energy against atomic number (elements 1-20)",
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  "yAxis": "ionization energy (kJ/mol)",
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At a low point — the crash that starts a new period KEY
At a peak — the highest point of its period
About halfway up its period's rise
It cannot be placed without measuring it
PTB-049 · hard · transfer · seq 19 · seed:U3-G3/pool[59] (= PTB-049 gateItems[2], James) kept VERBATIM — stem, key, all three distractors, feedback, explanations, and the five-row Group-2 density table; stage-1 flags WARN-class only (Group-2 densities fresh for 049; Be/Mg/Ba cross-scope mentions are trend instances elsewhere, never density data — memory-answerability nil); the discard-data foil is the row's teeth ('strongest seed of the row' per the placement); no NOTA/AOTA · mcq4
Claim: 'density increases down Group 2.' The table lists the five metals' density values, read from the top of the group to the bottom. Do the data support the claim?
FIGURE (data-table · stimulus) — title: "Claim: density increases down Group 2" · columns: ["Element", "Density (g/cm³)"] · rows: [["Be", "1.85"], ["Mg", "1.74"], ["Ca", "1.55"], ["Sr", "2.64"], ["Ba", "3.51"]] · style: "column table with the claim as a caption band"
raw spec
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Not fully — the first two steps fall, 1.85 to 1.74 to 1.55, before the values rise to 2.64 and 3.51. KEY
Yes — every value increases down the group.
No — every value decreases down the group.
Yes, once beryllium is set aside as a one-off exception — the remaining four values climb from magnesium to barium.
PTB-045 · hard · transfer · seq 20 · seed:U3-G3/pool[46] (= PTB-045 gateItems[1], James — the cross-family extrapolation critique) with the mandated must_freshen_instance + 2026-09-07 RECOVERY SWEEP (widened course instance rule): the metal half is now POSITIONAL ('the metal occupying the lowest position in Group 1') — every Group 1 name is 045-seen (Li/Na/K/Rb/Cs) or retired; tellurium kept (045-clean nonmetal half, no absolute-floor claim); foil b seed-VERBATIM class; foils c/d position-swapped; leftover sweep clean. — 2026-09-08 SOL WAVE 4 (sol loop-1 major: the nonmetal rule was applied without the stem designating tellurium's class, and Te is conventionally a metalloid): stem now designates it a nonmetal (sol's own remedy); everything else untouched — 2026-09-08 SOL WAVE 5 (sol loop-2 major: tellurium rejected as a nonmetal exemplar even with the wave-4 designation — conventionally a metalloid; sol's selenium swap would collide with the ADJACENT A#21 Ga/Ge/Se mass table): element abstracted away entirely — 'a nonmetal ... below the top of its own all-nonmetal column' (the A#17/B#20/E#20 register sol passes); all foil families carried · mcq4
The metal occupying the lowest position in Group 1 is predicted by the metal direction to be the group's most reactive metal. Reasoning the same way, a student concludes that a nonmetal sitting several rows below the top of its own all-nonmetal column must out-react every nonmetal above it in that column. Which response is correct?
The conclusion is wrong — nonmetals grow less reactive down a group, so that nonmetal is predicted to react less readily than the nonmetals above it, not more. KEY
The student is right — reactivity always increases toward the bottom of any group, for metals and nonmetals alike, so the bottom element is always the fiercest.
The student is wrong, because reactivity always decreases toward the bottom of any group — the Group 1 metal included.
The student is right about the lower nonmetal but wrong about the Group 1 metal.
PTB-050 · medium · application · seq 21 · authored (U3-G3 has zero prod seeds — blueprint directs an authored unlabeled-data-set identification capstone FRQ from PTB-050); case = rising Period-4 MASS table, the deliberate both-alternatives-share-the-direction scale-decided case (demo-2 class) · frq
A student reorganizing a chemistry class's old handouts finds a data sheet whose property-column heading has been torn away. The sheet lists three Period 4 elements — gallium, germanium, and selenium, in their left-to-right order across the period — beside the recorded values shown in the table.
FIGURE (data-table · stimulus) — title: "Property: ______ (label torn off)" · columns: ["Element", "Value"] · rows: [["Ga", "69.7"], ["Ge", "72.6"], ["Se", "79.0"]] · style: "torn-label table, Period 4 left-to-right order"
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A student reorganizing a chemistry class's old handouts finds a data sheet whose property-column heading has been torn away. The sheet lists three Period 4 elements — gallium, germanium, and selenium, in their left-to-right order across the period — beside the recorded values shown in the table. (a) Name the property the sheet most likely records. Justify your answer using BOTH the direction of the values along the row and the size of the values. (b) A classmate argues the sheet could just as well show electronegativity or ionization energy, since both of those also rise across a period. Rule out each of the two, citing for each one the cue that eliminates it. (c) The Period 4 element that sits between germanium and selenium was left off the sheet. Assuming the values keep changing steadily along the row, state the RANGE in which that element's value should fall, and justify the range.
Part a. Name the property the sheet most likely records. Justify your answer using BOTH the direction of the values along the row and the size of the values.
Model: Read the elements and their order first: gallium, germanium, and selenium run left to right across Period 4. Read the direction next: every value rises. Match the direction against the trends: rising across a period fits electronegativity, ionization energy, and atomic mass — while atomic radius falls across a period, so radius is out on direction alone. Check the size of the numbers: electronegativity's whole scale runs from about 0.7 to 4, and ionization energies are hundreds of kJ/mol — but these values are tens, with decimals, sitting exactly where these elements' atomic masses belong. Rising across the period, at the size of the elements' known masses — the torn label most likely said atomic mass. [Answer: atomic mass; also accepted: mass | the elements' atomic masses]
Part b. A classmate argues the sheet could just as well show electronegativity or ionization energy, since both of those also rise across a period. Rule out each of the two, citing for each one the cue that eliminates it.
Model: Both candidates do match the direction — so the value scale must decide. Electronegativity is out on scale: its whole scale runs from about 0.7 to 4, and no electronegativity is anywhere near 69.7. Ionization energy is out on scale too: ionization energies are hundreds of kJ/mol, far above values in the tens. So the direction alone cannot pick between them, but the size of the numbers eliminates both. [Answer: electronegativity fails the scale cue (its scale tops out near 4); ionization energy fails the scale cue (hundreds of kJ/mol, not tens); also accepted: both fit the rising direction but fail on size — EN is capped near 4, IE runs in the hundreds of kJ/mol]
Part c. The Period 4 element that sits between germanium and selenium was left off the sheet. Assuming the values keep changing steadily along the row, state the RANGE in which that element's value should fall, and justify the range.
Model: Along a steady run, an element's value is bracketed by the values of its two neighbors in the row. The missing element sits between germanium at 72.6 and selenium at 79.0. So its value should fall between 72.6 and 79.0 — the neighbors give a RANGE, not an exact number, and nothing in the trend justifies picking the exact midpoint. [Answer: between 72.6 and 79.0; also accepted: greater than 72.6 and less than 79.0 | 72.6 to 79.0, stated as a bounding range rather than a single predicted number]
Full model answer. (a) Read the elements and their order first: gallium, germanium, and selenium run left to right across Period 4. Read the direction next: every value rises. Match the direction against the trends: rising across a period fits electronegativity, ionization energy, and atomic mass — while atomic radius falls across a period, so radius is out on direction alone. Check the size of the numbers: electronegativity's whole scale runs from about 0.7 to 4, and ionization energies are hundreds of kJ/mol — but these values are tens, with decimals, sitting exactly where these elements' atomic masses belong. Rising across the period, at the size of the elements' known masses — the torn label most likely said atomic mass. [Answer: atomic mass; also accepted: mass | the elements' atomic masses] (b) Both candidates do match the direction — so the value scale must decide. Electronegativity is out on scale: its whole scale runs from about 0.7 to 4, and no electronegativity is anywhere near 69.7. Ionization energy is out on scale too: ionization energies are hundreds of kJ/mol, far above values in the tens. So the direction alone cannot pick between them, but the size of the numbers eliminates both. [Answer: electronegativity fails the scale cue (its scale tops out near 4); ionization energy fails the scale cue (hundreds of kJ/mol, not tens); also accepted: both fit the rising direction but fail on size — EN is capped near 4, IE runs in the hundreds of kJ/mol] (c) Along a steady run, an element's value is bracketed by the values of its two neighbors in the row. The missing element sits between germanium at 72.6 and selenium at 79.0. So its value should fall between 72.6 and 79.0 — the neighbors give a RANGE, not an exact number, and nothing in the trend justifies picking the exact midpoint. [Answer: between 72.6 and 79.0; also accepted: greater than 72.6 and less than 79.0 | 72.6 to 79.0, stated as a bounding range rather than a single predicted number]

Form B

PTB-033 · easy · recall · seq 1 · seed:U3-G3/pool[10] (= PTB-033 gateItems[1], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; zero stage-1 flags; anonymous atoms A/B, element-free · mcq4
Atom A's electron can be removed with little energy; removing atom B's takes far more. Which statement follows?
Atom B holds its outer electron more strongly than atom A holds its own. KEY
Atom B has more electrons than atom A.
Atom A's electron was already outside the atom.
Atom B releases more energy when its electron leaves.
PTB-037 · easy · recall · seq 2 · seed:U3-G3/pool[23] (PTB-037 gateItems[2]) VERBATIM — fluorine-highest-EN is 037's taught rule content (rule line 4), not an instance; expected stage-3 V-T7 material hit on 'fluorine' -> recorded scoped gate_config adjudication candidate (gate_config ships EMPTY; flag for David/James), stem/key grams expected covered by the rule-gram whitelist · mcq4
Fluorine has the highest electronegativity of all the elements. What does that tell you about fluorine atoms?
They pull electrons shared with another atom more strongly than any other kind of atom. KEY
They give away their outer electrons to other atoms more easily than any other kind of atom does.
They need more energy than any other atoms to lose an electron.
They are the largest atoms in the periodic table.
PTB-041 · easy · recall · seq 3 · seed:U3-G3.pool[35] (= PTB-041 gateItems[2], James) — VERBATIM; placement flags: freshness_scope_article WARN only (barium in 032/036/040/045/047/048, oxygen in 13 corpora, argon in 036/038/040/047 — none states these elements' metallic character; blind watch); stem HTML-stripped only · mcq4
In reactions, barium atoms readily give away two outer electrons, oxygen atoms pull in two extra electrons, and argon atoms do neither. Which element shows the strongest metallic character?
Barium KEY
Oxygen
Argon
They are equal, because all three involve two electrons or none
PTB-046 · easy · application · seq 4 · seed:U3-G3/pool[50] (= PTB-046 gateItems[2], James) STRUCTURE-KEPT with the instance freshened wholesale per must_freshen_instance + freshness_same_lesson (the lithium-to-fluorine Period-2 mass table is 046's own article extraNotes data set): placement's 'different period' route — four neighboring Period 5 elements In/Sn/Sb/Te with real standard atomic masses 114.8/118.7/121.8/127.6 (1-decimal style matching the lesson's own mass table); key text and distractor texts carried (non-instance), b/d feedback verbatim, c's count word adapted seven->four, explanations re-anchored to the fresh values · mcq4
The table lists the atomic masses of four neighboring Period 5 elements in order from indium to tellurium. What trend does the table show?
FIGURE (data-table · stimulus) — title: "Atomic masses across Period 5" · columns: ["Element", "Atomic mass"] · rows: [["In", "114.8"], ["Sn", "118.7"], ["Sb", "121.8"], ["Te", "127.6"]] · style: "plain data table, no annotations"
raw spec
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Atomic mass increases from left to right across the period. KEY
Atomic mass decreases from left to right across the period.
Atomic mass increases down a group.
The masses show no trend, because atomic mass is not a periodic property.
PTB-030 · medium · application · seq 5 · seed:U3-G3.pool[2] (= PTB-030 gateItems, James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson: fluorine is 030's own fluency instance): pair B/F -> B/C from the blueprint's free Period-2 space {B,C,N}; structure, key logic, and two of three foils kept · mcq4
Boron and carbon sit in Period 2, carbon farther right. Why is the carbon atom the smaller of the two?
Across the period the nuclear charge increases while the outer electrons stay in the same shell, so carbon's outer electrons are pulled in more strongly. KEY
Carbon's atoms have fewer electron shells than boron's.
Carbon's atoms weigh more than boron's, and the extra weight squeezes a heavier atom down into less space than a lighter atom takes up.
Boron's atoms are larger because metalloids always have larger atoms than nonmetals.
PTB-031 · medium · application · seq 6 · seed:U3-G3/pool[3] (= PTB-031 gateItems[0], James) — structure/misconceptions/logic kept; corpus-audit-forced instance freshen applied: nitrogen -> krypton, phosphorus -> xenon in every field; one micro-edit in d1's misconception ('share five valence electrons each' -> 'share the same valence count'); stage-1 keep-verbatim OVERRIDDEN (see row flags — validator-real cross-form rule vs kept seeds 5A/5C/14C) · mcq4
Krypton and xenon share a group, xenon one row lower. Which statement compares their atoms correctly, with the correct reason?
Xenon's atoms are larger, because their outer electrons occupy an added shell farther from the nucleus. KEY
Xenon's atoms are larger, because they hold more valence electrons.
Krypton's atoms are larger, because krypton's nucleus is lighter and holds its electrons loosely.
The two atoms are the same size, because groupmates behave alike.
PTB-032 · medium · application · seq 7 · seed:U3-G3/pool[8] (= PTB-032 gateItems[2], James) — structure/misconceptions kept; must_freshen_instance RESOLVED by the exact wholesale instance swap Al/Si/S (Period 3) -> Sr/In/Sn (Period 5) in every field; both blueprint candidates rejected on same-seq collisions (see notes) · mcq4
The periodic-table snippet highlights strontium, indium, and tin. Rank them from smallest to largest atomic radius.
FIGURE (periodic-table-snippet · stimulus) — highlightedCells: [{"symbol": "Sr", "period": 5, "group": 2}, {"symbol": "In", "period": 5, "group": 13}, {"symbol": "Sn", "period": 5, "group": 14}] · context: "full table outline with only the three highlighted cells carrying symbols" · style: "clean deterministic SVG table outline; highlighted cells share one color; no other symbols printed; no trend arrows" · blindDescription: "A periodic-table outline with exactly three highlighted cells, all in one row: the cell labeled Sr near the left edge of the table, and the cells labeled In…
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 }
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Smallest to largest: tin, indium, strontium. KEY
Smallest to largest: strontium, indium, tin.
All three have the same atomic radius, because they sit in the same period.
They cannot be ranked without measured values.
PTB-034 · medium · application · seq 8 · seed:U3-G3/pool[12] (= PTB-034 gateItems[0], James) — structure/misconceptions kept; stage-1 must_freshen_instance resolved by the wholesale pair swap Al/S -> Sr/Sb (Period 3 -> Period 5, third -> fifth shell); stem's first sentence restructured to break the 'farther right. Which statement' boundary gram shared with kept seed 5A; question clause + options verbatim mod instance; feedback-leftover sweep clean · mcq4
Antimony sits farther right than strontium in Period 5. Which statement compares their ionization energies correctly, with the correct reason?
Antimony's is generally higher, because the greater nuclear charge pulls its same-shell outer electrons in more strongly. KEY
Antimony's is higher, because its outer electrons sit farther from the nucleus, where they are harder to reach.
Strontium's is higher, because metals resist losing electrons.
The two are equal, because both atoms' outer electrons occupy the fifth shell.
PTB-035 · medium · application · seq 9 · seed:U3-G3/pool[16] (= PTB-035 gateItems[1], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; stage-1 flags: freshness_scope_article WARN only (oxygen/selenium cross-scope — no scope article states the O-vs-Se ionization comparison); 'Group 16' = seed-carried positional label with a SAME-LESSON number hit (035's own FL2 says 'Group 16') — the gate's flagged numeric-scan adjudication candidate, recorded in flags · mcq4
Oxygen holds the top spot in its group, and selenium sits two rows below it. From which atom does it take less energy to remove one electron, and why?
Selenium — down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly. KEY
Oxygen — smaller atoms hold their electrons more loosely.
Selenium — its bigger nuclear charge pushes the outer electrons away from the nucleus, so they come off with almost no added energy.
Oxygen — atoms with fewer shells lose electrons more easily.
PTB-036 · medium · application · seq 10 · seed:U3-G3.pool[19] (= PTB-036 gateItems, James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson: beryllium+oxygen are 036's own check-set instances): triple Be/C/O -> Ga/Ge/As from the blueprint's licensed free space ('Period-4 main-group Ga/Ge/As — values do rise generally'); structure, key logic, and all three foil families kept · mcq4
Gallium, germanium, and arsenic sit side by side in Period 4, in that order from left to right. Rank them from lowest to highest ionization energy.
Gallium, germanium, arsenic KEY
Arsenic, germanium, gallium
Germanium, gallium, arsenic
Gallium, arsenic, germanium
PTB-038 · medium · application · seq 11 · seed:U3-G3/pool[25] (PTB-038 gateItems[1], James) — FRESHENED, stage-2 judgment call FLAGGED FOR DAVID/JAMES: pair Ca/Br (Period 4) -> Sr/Sb (Period 5) because PTB-040's student-seen K/Ca/Br Period-4 fluency hands the seed's exact ask ('Which of the three pulls shared electrons the most strongly? -> Bromine'); structure, key logic, all foil classes and feedback clauses kept verbatim modulo the instance swap; Sr/Sb carry no EN content anywhere in scope; no values printed · mcq4
Strontium sits near the left end of Period 5 and antimony well to its right. Which pulls shared electrons more strongly, and why?
Antimony, because across a period the nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly — and a stronger pull also acts on shared electrons. KEY
Strontium, because metal atoms hold every one of their electrons more tightly than nonmetal atoms do, and an atom with a tighter grip on its own electrons must also exert a stronger pull on the electrons it shares.
Antimony, because its atoms have more electron shells than strontium's, and more shells always mean a stronger pull on shared electrons.
They pull equally strongly, because both sit in Period 5 and share the same outer shell, so their pulls on shared electrons match.
PTB-039 · medium · application · seq 12 · seed:U3-G3/pool[29] (PTB-039 gateItems[2]) VERBATIM — WARN-class flags only (Ba/Be fresh for 039; real Pauling values 0.89/1.57 seed-carried); two-value assignment facet; 12B/13B beryllium adjacency FLAGGED in authoring_notes (13B's licensed Be/B/N run — resolve at assembly) · mcq4
Beryllium sits at the top of Group 2 and barium near the bottom. One of them has electronegativity 1.57 and the other 0.89. Which value belongs to barium, and why?
0.89, because down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly — and a weaker hold means a weaker pull on shared electrons. KEY
1.57, because barium's far bigger nuclear charge must give it the stronger pull on shared electrons, so the larger of the two numbers has to belong to barium rather than beryllium.
1.57, because heavier atoms always hold electrons more tightly.
Neither — Group 2 metals are not assigned electronegativities.
PTB-040 · medium · application · seq 13 · seed:U3-G3/pool[32] (PTB-040 gateItems[2]; must_freshen_instance + freshness_same_lesson applied: carbon/oxygen are 040's own WE-reuse instances) — freshened Period-2 B/C/N/O -> Period-5 Sr/In/Sn (the ONLY P5 free triple after form C's claims and 040-seen Te; blueprint's Be/B/N candidate rejected: Be would repeat ADJACENT to 12B's kept Ba/Be seed and same-seq with 13A — deviation recorded); seed foil classes kept (direction-backwards / adjacent-swap / shuffle); end positions stated in-stem (pool[29] cushion style); real EN monotonic Sr 0.95 < In 1.78 < Sn 1.96, values not printed; seed pt-snippet figure dropped (same call as form A); leftover sweep clean · mcq4
Strontium, indium, and tin all occupy Period 5, strontium farthest left of the three and tin farthest right. Rank them from lowest to highest electronegativity.
Strontium, indium, tin KEY
Tin, indium, strontium
Strontium, tin, indium
Indium, strontium, tin
PTB-042 · medium · application · seq 14 · seed:U3-G3/pool[36] (= PTB-042 gateItems, James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; stage-1 flags: freshness_scope_article WARN only (Ca/Se fresh for 042; Ca in 041's fluency give/take classify, Se in 035's seed — neither states the Ca-vs-Se metallic comparison) · mcq4
Calcium and selenium both sit in Period 4. A student claims selenium is the more metallic because its atoms have more outer electrons to offer. Which response is correct?
Calcium is more metallic — across a period the nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly and are harder to give away, and selenium sits farther right. KEY
The student is right — the more outer electrons an atom has to offer, the more of them it can give away in reactions, so selenium, with six outer electrons on offer, must be more metallic than calcium, which has only two to give.
Selenium is more metallic because its atoms are smaller, and smaller atoms give their electrons away more easily.
The two are equally metallic, because elements in the same period always share the same character, and both sit in Period 4.
PTB-043 · medium · application · seq 15 · seed:U3-G3/pool[40] (= PTB-043 gateItems[1], James) — INSTANCE-FRESHENED (stage-1 keep overridden, see flags: kept 9A holds nitrogen + '15' + the 'top of Group 15' grams, a triple cross-form FAIL): nitrogen -> boron, bismuth -> thallium, 'Group 15' -> digit-free 'its group / the same group'; structure, key logic, and all four foil families byte-preserved modulo the swap; boron/thallium untracked, zero same-lesson hits; facts verified (Group 13 ends; IE B 801 > Tl 589 kJ/mol, not printed) — 2026-09-08 SOL WAVE 4 (sol loop-1 major: thallium is NOT at Group 13's very bottom — nihonium sits below it): positions recast as relative ('four rows below'), options keyed to the element names; foil families (top-inverted / right-pick-wrong-reason / all-equal) preserved · mcq4
Boron sits at the top of its group and thallium sits four rows below it in the same group. Of these two, which shows the stronger metal behavior, and why?
Thallium — down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly and are easier to give away. KEY
Boron — the smallest atom of a group always behaves most like a metal.
Thallium — but only because heavier atoms are always more metallic: the extra mass is what makes an element shiny, dense, and able to conduct like a metal.
Neither — every element in a group shows the same metal behavior.
PTB-048 · medium · application · seq 16 · seed:U3-G3/pool[55] (= PTB-048 gateItems[1], James) STRUCTURE-KEPT, instance freshened wholesale per must_freshen_instance + freshness_same_lesson (Ca/Sr/Ba radii 197/215/224 pm = 048's own gate/extraNotes set): Group 12 densities, rising — Zn 7.14 / Hg 13.53 quoted in the stem (seed's no-figure shape); key sentence and averaging foil carried VERBATIM (instance-free; key = article rule line 2, A3 runtime-whitelist class); flat-group and not-justified foils re-anchored to density; feedbacks verbatim-with-swaps; measured Cd 8.65 in the explanation — 2026-09-08 BLIND WAVE 3 (r1 F1/F2 + circularity): 'Why is the prediction justified?' -> 'Under what condition...' — the item no longer asserts a steady trend it never evidenced (two data points cannot show steadiness, and using cadmium's own value would be circular); the key is now the CONDITION itself (the lesson's rule), the averaging/flat-group/give-up foil families carried as condition-shaped variants — 2026-09-08 WAVE 3d (sol4 advisory, re-blind round: 'only if' overclaims necessity — the taught rule is a SUFFICIENT condition): key and flat-group foil soften to 'If ...'; ask, foils b/d, and explanation unchanged · mcq4
Zinc's density is 7.14 g/cm³ and mercury's is 13.53 g/cm³, and cadmium sits between them in Group 12. A chemist predicts cadmium's density lies between 7.14 and 13.53 g/cm³. Under what condition is the prediction justified?
If the group's densities change steadily down the column — a steady trend places the middle element's value between its neighbors' values. KEY
No condition is needed — averaging the values of any two elements always gives exactly the value of the element that sits between them in the table.
If all Group 12 elements have nearly the same density.
No condition can justify it — a density can never be predicted without measuring it.
PTB-044 · hard · transfer · seq 17 · seed:U3-G3.pool[42] (= PTB-044 gateItems, James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson: tellurium/oxygen are 044's own): pair Te/O -> As/P, the one Group-15 pair whose real-world reactivity order matches the taught trend cleanly ('different pair from form A' per the blueprint); claim structure, key logic, and all three foil families kept — 2026-09-08 SOL WAVE 4 (sol loop-1 major, same class as A#20: arsenic is conventionally a metalloid and the stem never licensed the nonmetal rule): stem now designates both elements nonmetals and states the taught reaction mode (the E#17 construction sol passed); key/foils untouched — 2026-09-08 SOL WAVE 5 (sol loop-2 major: arsenic rejected as a nonmetal exemplar even with the wave-4 designation; O/S/Te = PTB-044's own check ladder and N/P would clone E#17): pair abstracted to nonmetals R/T in a stipulated all-nonmetal group (letters dodge B#20's M/J/Q within form B); bigger-atom claim, all three foil families, and the taught mechanism carried; 'exactly three extra electrons' generalized to 'the same number' (no group commitment) · mcq4
Nonmetals R and T share one all-nonmetal group, and R sits two rows below T, so R's atoms are bigger. A student claims R should be more reactive than T because its bigger atoms 'have more room for extra electrons'. Both react by pulling in extra electrons. Which response is correct?
R is less reactive — a nonmetal atom reacts by pulling in extra electrons, and it reacts more easily when that pull is stronger; R's outer shell sits farther from the nucleus, so its pull on an incoming electron is weaker. KEY
The student is right — R's bigger atoms sweep up passing electrons over a larger surface, so they catch extra electrons more often and react faster than T's smaller atoms can.
The student is right that R is more reactive, but the reason is its bigger nuclear charge — a nucleus with that many more protons must pull incoming electrons in far more strongly than T's smaller nucleus can.
The two react equally readily, because their atoms need the same number of extra electrons to fill the outer shell.
PTB-047 · hard · transfer · seq 18 · seed:U3-G3/pool[51] (= PTB-047 gateItems[0], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation, figureSpec (blindDescription added — authoring-side interim, see flags); stage-1 flags ['freshness_scope_article'] only; stem/options element-free; feedback carries the reference graph's own plotted values 2081/496 (recorded expected observation — see row flags); stem '1 through 20' = recorded numeric adjudication candidate · mcq4
A student looks at the graph of ionization energy against atomic number for elements 1 through 20 and claims the values simply rise as atomic number grows. Which reading of the graph is correct?
FIGURE (data-graph · stimulus) — title: "Ionization energy against atomic number (elements 1-20)" · xAxis: "atomic number" · yAxis: "ionization energy (kJ/mol)" · points: "H 1312, He 2372, Li 520, Be 899, B 801, C 1086, N 1402, O 1314, F 1681, Ne 2081, Na 496, Mg 738, Al 578, Si 786, P 1012, S 1000, Cl 1251, Ar 1521, K 419, Ca… · annotations: ["element symbols labeled at peaks and valleys"] · style: "line plot, points joined in atomic-number order" · blindDescription: "A line graph plotting one point per element, joined in atomic-number order across the plotted range. The curve climbs to a sharp labeled peak, drops steeply…
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The values rise within each period but crash at the start of the next — the pattern repeats rather than climbing. KEY
The student is right — every element has more protons than the one before it, so each value plotted on the graph must be higher than the last.
The values fall steadily as atomic number grows.
The values change at random, with no pattern.
PTB-049 · hard · transfer · seq 19 · seed:U3-G3/pool[58] (= PTB-049 gateItems[1], James) STRUCTURE-KEPT with the mandated must_freshen_instance + freshness_same_lesson applied: Ar/K (39.95/39.10, Z 18/19 — 049's own article reversal) -> COBALT/NICKEL (58.93/58.69), the placement's first-listed fresh route and the only scan-clean real pair reversal (Te/I blocked: iodine 049-seen, tellurium 045-seen + 4 WARNs; Co/Ni in zero scope corpora); Z column DROPPED from the figure because nickel's 28 is a 049 same-lesson number (cesium's melting point) — Z-order stated in words instead; foil b's 'close to 39' -> 'nearly equal' ('59' is also 049-own); foil c 'wrong column' -> 'wrong quantity' (no Z column remains); foil d + feedback kept VERBATIM (substantive always-untestable escape hatch, recorded watch class); explanation's historical closer hedged to 'one of the' (Co/Ni is genuinely one of the canonical reversals) · mcq4
Claim: 'atomic mass always increases as atomic number increases.' The table gives the atomic masses of cobalt and nickel; nickel sits one place after cobalt in the modern periodic table. Do the data support the claim?
FIGURE (data-table · stimulus) — title: "Claim: atomic mass always increases with atomic number" · columns: ["Element", "Atomic mass"] · rows: [["Co", "58.93"], ["Ni", "58.69"]] · style: "two-row table with the claim as a caption band" · note: "elements listed in order of increasing atomic number"
raw spec
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No — this pair breaks the claim: nickel has the higher atomic number but the lower mass, 58.69 against cobalt's 58.93. KEY
Yes — nickel comes after cobalt and the two masses are nearly equal.
Yes — the atomic number increases from cobalt to nickel, and an increase in atomic number is exactly what the claim describes.
The data cannot test an 'always' claim.
PTB-045 · hard · transfer · seq 20 · seed:U3-G3/pool[47] (= PTB-045 gateItems[2], James — the dual-family consistent-statement 2x2) with ALL FOUR instances freshened; 2026-09-07 RECOVERY SWEEP (widened course instance rule): the Group 2 bottom instance is now the anonymous metal M — extending the item's own J/Q anonymous-nonmetal device — because every classroom-safe Group 2 name is 045-seen (Ba/Ca/Mg) or form-B-loaded (Sr at 7/8/11/13; Ba+Be at 12B); beryllium kept as the named top anchor; the seed's 2x2 option algebra and foil d feedback kept verbatim-class. · mcq4
A metal, M, sits far below beryllium in Group 2. In another column of the periodic table, nonmetal J sits at the top and nonmetal Q sits far below it. Which statement is correct?
M is more reactive than beryllium, and J is more reactive than Q. KEY
M is more reactive than beryllium, and Q is more reactive than J.
Beryllium is more reactive than M, and J is more reactive than Q.
Beryllium is more reactive than M, and Q is more reactive than J.
PTB-050 · medium · application · seq 21 · authored (blueprint FRQ case: graph cases carry all load-bearing facts in stem text — no structural blind family for property-vs-atomic-number graphs; pool-53/60 pattern); case = the demo-0 sawtooth SHAPE re-keyed to ATOMIC RADIUS via period-START peaks (the contrast pool-60's own radius distractor teaches); element-free by construction — 2026-09-08 BLIND WAVE 3 (r1 cross-item leak: B#18 explicitly supplies the IE peak pattern part (b) asked students to cite): part (b) candidates -> electronegativity + atomic mass; EN is eliminated by the value SCALE, which no sibling B item supplies; part (a), part (c), the IE scale-mention inside part (a)'s justification, and the IE-misread graderDiagnostic are untouched — 2026-09-08 SOL WAVE 4 (sol loop-1 major: the rubric required an exceptionless mass-rise claim, but Ar->K reverses inside elements 1-20 and PTB-049 teaches the reversal class): the mass elimination now rests on the absence of repeating period-start peaks and long slides, with the taught tiny one-step reversals acknowledged; element-free phrasing (no new instance tokens) · frq
A wall poster in a science room has lost its caption. It shows a line graph of some property plotted against atomic number for elements 1 through 20, but the vertical axis is numbered without a name or a unit. The line rises and falls in a repeating pattern: the peaks sit at atomic numbers 3, 11, and 19, each peak is a little higher than the one before it, the plotted values run from a few tens up to about 230, and after each peak the values generally slide downward until the line jumps sharply up to the next peak.
A wall poster in a science room has lost its caption. It shows a line graph of some property plotted against atomic number for elements 1 through 20, but the vertical axis is numbered without a name or a unit. The line rises and falls in a repeating pattern: the peaks sit at atomic numbers 3, 11, and 19, each peak is a little higher than the one before it, the plotted values run from a few tens up to about 230, and after each peak the values generally slide downward until the line jumps sharply up to the next peak. (a) Name the property the graph most likely plots. Justify your answer using BOTH the positions of the peaks in the repeating pattern and the size of the plotted values. (b) A classmate suggests the poster might instead show electronegativity or atomic mass. Rule out each of the two, citing for each one the cue that eliminates it. (c) The poster's pattern is claimed to continue beyond the plotted range. The element with atomic number 37 begins Period 5. If the pattern holds, where should that element's point land on the graph — and how high, compared with the peaks already plotted? Justify your placement.
Part a. Name the property the graph most likely plots. Justify your answer using BOTH the positions of the peaks in the repeating pattern and the size of the plotted values.
Model: Read the pattern first: the peaks sit at atomic numbers 3, 11, and 19 — each of those is the FIRST element of a new period. Match the pattern against the trends: atomic radius peaks exactly there — a period's first element has just added a new outer shell, making it the biggest atom of its period, and radius then falls across the period as the growing nuclear charge pulls the outer electrons in more strongly. The rising peaks fit too: atoms grow down a group, so each period's first element starts bigger than the one before it. Check the size of the numbers: values from a few tens up to about 230 sit right where radii live — near a hundred picometers — while ionization energies run in the hundreds and thousands of kJ/mol and electronegativity never leaves its roughly 0.7-to-4 scale. Peaks at each period's first element, on a picometer-sized scale — the caption most likely said atomic radius. [Answer: atomic radius; also accepted: radius | the size of the atoms (atomic radius)]
Part b. A classmate suggests the poster might instead show electronegativity or atomic mass. Rule out each of the two, citing for each one the cue that eliminates it.
Model: Electronegativity fails on scale: its values never leave the roughly 0.7-to-4 scale, while this graph's values run from a few tens up to about 230 — far too large. Its high points would also sit in the wrong place: the strongest pullers sit toward each period's END, so its peaks come just before each jump, not at atomic numbers 3, 11, and 19. Atomic mass fails on shape: it climbs with atomic number in a nearly steady rise — the course's rare taught reversals are tiny, one-step dips where a neighbor pair swaps order by a whisker — and it never makes a repeating pattern of period-start peaks followed by long downward slides. So the value scale eliminates electronegativity and the shape eliminates atomic mass. [Answer: electronegativity is out because its values never leave the roughly 0.7-to-4 scale, far below values running up to about 230; atomic mass is out because it rises almost steadily — its rare taught reversals are tiny one-step dips — and never shows repeating period-start peaks with long downward slides; also accepted: electronegativity fails the scale (0.7-to-4, not tens up to 230) — its high points also sit late in each period, not at 3/11/19; atomic mass makes no sawtooth — its rise has only tiny one-step reversals, never repeating peaks and slides]
Part c. The poster's pattern is claimed to continue beyond the plotted range. The element with atomic number 37 begins Period 5. If the pattern holds, where should that element's point land on the graph — and how high, compared with the peaks already plotted? Justify your placement.
Model: In this pattern, every element that begins a new period sits at a peak: a just-added outer shell makes it the biggest atom of its period. Atomic number 37 begins Period 5, so its point lands at a NEW PEAK, not on a slide or at a low point. And because atoms grow down a group, each period's first element starts bigger than the one before — the plotted peaks already climb from one to the next — so the new peak should sit HIGHER than the peak at atomic number 19. [Answer: at a new peak, higher than the peak at atomic number 19; also accepted: at a peak (a period-start element, the largest of its period), topping the previous peaks | a peak above the one at 19, continuing the climb of the peaks]
Full model answer. (a) Read the pattern first: the peaks sit at atomic numbers 3, 11, and 19 — each of those is the FIRST element of a new period. Match the pattern against the trends: atomic radius peaks exactly there — a period's first element has just added a new outer shell, making it the biggest atom of its period, and radius then falls across the period as the growing nuclear charge pulls the outer electrons in more strongly. The rising peaks fit too: atoms grow down a group, so each period's first element starts bigger than the one before it. Check the size of the numbers: values from a few tens up to about 230 sit right where radii live — near a hundred picometers — while ionization energies run in the hundreds and thousands of kJ/mol and electronegativity never leaves its roughly 0.7-to-4 scale. Peaks at each period's first element, on a picometer-sized scale — the caption most likely said atomic radius. [Answer: atomic radius; also accepted: radius | the size of the atoms (atomic radius)] (b) Electronegativity fails on scale: its values never leave the roughly 0.7-to-4 scale, while this graph's values run from a few tens up to about 230 — far too large. Its high points would also sit in the wrong place: the strongest pullers sit toward each period's END, so its peaks come just before each jump, not at atomic numbers 3, 11, and 19. Atomic mass fails on shape: it climbs with atomic number in a nearly steady rise — the course's rare taught reversals are tiny, one-step dips where a neighbor pair swaps order by a whisker — and it never makes a repeating pattern of period-start peaks followed by long downward slides. So the value scale eliminates electronegativity and the shape eliminates atomic mass. [Answer: electronegativity is out because its values never leave the roughly 0.7-to-4 scale, far below values running up to about 230; atomic mass is out because it rises almost steadily — its rare taught reversals are tiny one-step dips — and never shows repeating period-start peaks with long downward slides; also accepted: electronegativity fails the scale (0.7-to-4, not tens up to 230) — its high points also sit late in each period, not at 3/11/19; atomic mass makes no sawtooth — its rise has only tiny one-step reversals, never repeating peaks and slides] (c) In this pattern, every element that begins a new period sits at a peak: a just-added outer shell makes it the biggest atom of its period. Atomic number 37 begins Period 5, so its point lands at a NEW PEAK, not on a slide or at a low point. And because atoms grow down a group, each period's first element starts bigger than the one before — the plotted peaks already climb from one to the next — so the new peak should sit HIGHER than the peak at atomic number 19. [Answer: at a new peak, higher than the peak at atomic number 19; also accepted: at a peak (a period-start element, the largest of its period), topping the previous peaks | a peak above the one at 19, continuing the climb of the peaks]

Form C

PTB-033 · easy · recall · seq 1 · seed:U3-G3/pool[11] (= PTB-033 gateItems[2], James) — structure/key/misconceptions kept; stage-1-licensed opportunistic freshen applied: sodium -> manganese in every field (stem recast to the course's 'one electron' phrasing; feedback-leftover sweep clean) · mcq4
A student writes: 'When one electron is removed from a manganese atom, the atom releases its ionization energy.' What is wrong?
Ionization energy is energy that must be supplied to remove the electron — the removal releases nothing. KEY
Nothing — an atom gives off its ionization energy at the moment it loses an electron.
The statement fails only because manganese has no ionization energy.
The statement fails because a manganese atom's electron cannot be removed at all.
PTB-037 · easy · recall · seq 2 · seed:U3-G3/pool[22] (PTB-037 gateItems[1]; must_freshen_instance applied: value triple freshened wholesale Br 2.96 / I 2.66 / H 2.20 -> Ag 1.93 / Fe 1.83 / Zn 1.65, real Pauling values, hydrogen out per SEED RULING; structure and foil classes verbatim, feedback/explanation re-instanced; values corpus-audited against the scope's full student-seen decimal inventory, elements Zn/Ag corpus-clean + Fe cross-scope WARN only) · mcq4
Silver's electronegativity is 1.93, iron's is 1.83, and zinc's is 1.65. Which of the three pulls shared electrons the least strongly?
Zinc KEY
Silver
Iron
They pull equally, because all three can share electrons
PTB-041 · easy · recall · seq 3 · seed:U3-G3.pool[33] (= PTB-041 gateItems[0], James) — VERBATIM; placement flags: freshness_scope_article WARN only (osmium zero-hit outside this seed; lithium in 17 corpora — none ties lithium to metallic character vs density; blind watch); stem HTML-stripped only; critique-facet rotation within the row recorded (blueprint case_target) · mcq4
Osmium is far denser than lithium, so a student concludes that osmium must have far stronger metallic character. What is wrong with the reasoning?
Metallic character is about how easily atoms give away their outer electrons, not about how dense the element is. KEY
Nothing — the denser of two metals is always the more metallic, because packing more mass into each cubic centimeter is exactly what metal behavior means.
The property compared should have been shininess, not density.
Density does measure metallic character, but lithium is denser than osmium.
PTB-046 · easy · application · seq 4 · seed:U3-G3/pool[49] (= PTB-046 gateItems[1], James) STRUCTURE-KEPT — the reversed-listing trap is 046's taught sub-skill and is KEPT per the placement; instance freshened wholesale per must_freshen_instance + freshness_same_lesson (Group-1 IE with cesium/lithium 376/520 kJ/mol = 046's own worked example): fresh instance = the three Group 12 metals' boiling points listed bottom-of-group first (Hg 357, Cd 767, Zn 907 °C — real, strictly monotonic by position, all positive so no overlap with 19C's negative-sign case); zinc/cadmium/mercury scan CLEAN across all 21 scope lessons (the cleanest family in the corpus); trap mechanics identical: values rise down the reversed LIST while the property falls down the GROUP; option and feedback texts carried with the property/instance swapped — 2026-09-08 BLIND WAVE 3 (r1 F1/F2 two-defensible: the group order was never supplied, so 'top of the group' was unanchored): stem now states the group order (Zn top / Cd / Hg bottom) BEFORE the reversed-LIST table; the taught trap (listing order vs group order) is untouched and now answerable · mcq4
In Group 12, zinc sits at the top of the group, cadmium below it, and mercury at the bottom. This table lists the three Group 12 metals from mercury at the top of the list to zinc at the bottom, with their boiling points. What trend does the table show?
FIGURE (data-table · stimulus) — title: "Boiling points of the Group 12 metals" · columns: ["Element", "Boiling point (°C)"] · rows: [["Hg", "357"], ["Cd", "767"], ["Zn", "907"]] · style: "plain data table, no annotations; note the reversed element order" · note: "elements listed bottom-of-group first"
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Boiling point decreases from the top of the group to the bottom. KEY
Boiling point increases from the top of the group to the bottom.
Boiling point shows no trend in this group.
Boiling point decreases and then increases down the group.
PTB-030 · medium · application · seq 5 · seed:U3-G3.pool[1] (= PTB-030 gateItems, James) — VERBATIM; placement flags: freshness_scope_article WARN only (B/N in 032's article; N in 036/037/039 — none states the B-vs-N radius comparison; blind watch) · mcq4
A student writes: 'Nitrogen's atoms must be bigger than boron's, because nitrogen's atoms hold more electrons.' Both elements are in Period 2. What is wrong with the reasoning?
The extra electrons join the same shell while the growing nuclear charge pulls it in harder — nitrogen's atoms are the smaller ones. KEY
Nothing — more electrons do make a same-period atom larger.
The reasoning fails only because nitrogen actually holds fewer electrons than boron does, not more of them as the student said.
The reasoning fails because electrons take up no space at all.
PTB-031 · medium · application · seq 6 · seed:U3-G3/pool[4] (= PTB-031 gateItems[1], James) — structure/misconceptions/logic kept; stage-1 must_freshen_instance applied as germanium/lead (Group 14, two rows), REPLACING the corpus-blocked F->Br candidate (see row flags); instance swap selenium -> lead, oxygen -> germanium in every field; two micro-edits: stem softening ('in fact much larger' -> 'in fact larger') and a key re-phrase ('and lead's outer electrons sit' -> 'and the outer electrons of lead sit') dodging PTB-043's WE gram 'lead's outer electrons' (deterministic corpus hit found by the check script) · mcq4
A student objects: 'Lead has far more protons than germanium, and more protons pull electrons in harder — so lead's atoms should be smaller.' The two share a group, and lead's atoms are in fact larger. Which reply gives the course's account?
Each row down the group adds an electron shell, and the outer electrons of lead sit in a much farther shell, held more weakly. KEY
Lead's protons each carry a weaker charge than germanium's protons do, so the nucleus's pull never grows.
Lead's atoms are larger because they hold more valence electrons.
The student is right, and measured sizes must be wrong.
PTB-032 · medium · application · seq 7 · seed:U3-G3/pool[6] (= PTB-032 gateItems[0], James) — structure/misconceptions kept; must_freshen_instance RESOLVED by the exact instance swap C/Si/Ge -> Cu/Ag/Au (row01-ledger-reserved Group-11 route; classroom Cu+Ag); d-foil feedback + keyExplanation RECAST for Group-11 measured-data honesty (Au sits smaller than Ag in modern tables — no field may assert the full downward rank; the smallest-pick key stays true in model AND data) · mcq4
The periodic-table snippet highlights copper, silver, and gold. Which element has the smallest atomic radius?
FIGURE (periodic-table-snippet · stimulus) — highlightedCells: [{"symbol": "Cu", "period": 4, "group": 11}, {"symbol": "Ag", "period": 5, "group": 11}, {"symbol": "Au", "period": 6, "group": 11}] · context: "full table outline with only the three highlighted cells carrying symbols" · style: "clean deterministic SVG table outline; highlighted cells share one color; no other symbols printed; no trend arrows" · blindDescription: "A periodic-table outline with exactly three highlighted cells, all in one column in the middle region of the table, in consecutive rows: the cell labeled Cu…
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Copper KEY
Gold
Silver
All three are the same size.
PTB-034 · medium · application · seq 8 · seed:U3-G3/pool[13] (= PTB-034 gateItems[1], James) — structure/misconceptions kept; stage-1 must_freshen_instance resolved by the PURE instance swap P/Mg -> Se/K in every field (Period 3 -> Period 4); different fresh pair from form B's per the stage-1 note; feedback-leftover sweep clean · mcq4
A student explains selenium's higher ionization energy this way: 'Selenium grips its electrons harder than potassium because its outer electrons sit farther from the nucleus.' Both elements are in Period 4. What is wrong with the explanation?
Across a period the outer electrons stay in the same shell — selenium's sit closer, and that stronger pull is what makes removal costly. KEY
Nothing — greater distance from the nucleus does make electrons harder to remove.
The explanation fails only because potassium and selenium sit in different periods.
The explanation fails because selenium's ionization energy is actually lower than potassium's, not higher as the student assumed.
PTB-035 · medium · application · seq 9 · seed:U3-G3/pool[15] (= PTB-035 gateItems[0], James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson: barium is 035's own FL1 instance): barium -> strontium in every field; beryllium KEPT (stage-1 note 'beryllium may stay'); structure, key logic, and all four foil families byte-preserved modulo the instance swap; strontium = ONE cross-scope WARN (048's radius table — no ionization content, memory-answerability nil); facts verified (Sr three rows below Be; real IE Be 899 > Sr 549 kJ/mol, values not printed) · mcq4
A student notices that strontium atoms have many more protons than beryllium atoms, and concludes that strontium must have the higher ionization energy of the two Group 2 elements. Which response is correct?
Strontium's ionization energy is lower — down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly. KEY
The student is right — strontium's much larger number of protons pulls every electron in more strongly, so removing an electron from strontium must take more energy than from beryllium.
Strontium's ionization energy is lower because strontium has fewer protons in its nucleus than beryllium.
The two ionization energies are equal, because both atoms have two outer electrons.
PTB-036 · medium · application · seq 10 · seed:U3-G3.pool[20] (= PTB-036 gateItems, James) — FRESHENED per placement flags + 2026-09-07 RECOVERY SWEEP (widened course instance rule): rubidium (James's own unflagged instance) KEPT as the ranked element; the comparison element is now POSITIONAL ('the Group 1 metal one row above it') because every other Group 1 name is 036-seen (Li/Na/K/Cs) or retired by the instance rule; critique structure, key logic, and all three foil classes preserved. · mcq4
A student ranks rubidium's ionization energy above that of the Group 1 metal one row above it, arguing that rubidium has more electrons than its upper neighbor. Which response is correct?
The ranking is backwards — ionization energy decreases from top to bottom down a group, so the metal above rubidium has the higher ionization energy. KEY
The student is right — an atom with more electrons always needs more energy to lose one, so rubidium's larger electron count puts its ionization energy above its upper neighbor's.
The two are equal, because both elements sit in Group 1.
The ranking is right, but the reason should be that rubidium has more protons.
PTB-038 · medium · application · seq 11 · seed:U3-G3/pool[26] (PTB-038 gateItems[2], James) — FRESHENED per mandated must_freshen_instance + freshness_same_lesson, with the stage-1 B/C/N candidate route REJECTED as memory-answerable (037 WE0 binds N 3.04 / C 2.55 verbatim; 049 FL2 carries the 2.04/2.55/3.04 ladder): run Be/B/C/N 1.57/2.04/2.55/3.04 -> In/Te 1.78/2.1 (real Pauling values, the audit's only clean same-period pair); seed ask shape kept ('... in some order. Which element has the value <top>?'); the two dropped element picks replaced by the two taught statement foils (equal-pull, cannot-be-matched) — 2026-09-08 BLIND WAVE 3 (r1 MAJOR cross-item leak: In 1.78 / Te 2.1 are exactly C#21's header-lost FRQ endpoints — this item handed the FRQ its part-(a) property and part-(c) range): instance -> gallium/arsenic, Period 4 (real Pauling 1.81/2.18; both families already adjudicated on this gate: period4-gallium, group15-arsenic); seed ask shape and both taught statement foils carried · mcq4
Gallium and arsenic both sit in Period 4, with arsenic farther right. Their electronegativities are 1.81 and 2.18, in some order. Which element has the value 2.18?
Arsenic KEY
Gallium
Neither — the two pull equally strongly, because both sit in Period 4
Either one — the values cannot be matched to the elements from their positions
PTB-039 · medium · application · seq 12 · seed:U3-G3/pool[28] (PTB-039 gateItems[1]) with the mandated must_freshen_instance + 2026-09-07 RECOVERY SWEEP (widened course instance rule): the bottom-of-group instance is replaced by potassium framed positionally ('two of the group's metals above it') — potassium is the only classroom-safe alkali that is not 039-seen (Li/Cs 039-seen) and does not collide at seq 12 (12A carries rubidium+sodium); foil classes kept verbatim-class (protons-only, same-group-equal, no-measurement escape); K corpus footprint (8C item, 048-article IE value) = recorded WARN. · mcq4
Potassium sits in Group 1, with two of the group's metals above it. Predict potassium's electronegativity compared with those metals above it.
The lowest of the three, because down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly — and a weaker hold means a weaker pull on shared electrons. KEY
The highest of the three, because potassium has the most protons of the three, and the pull of all those protons must reach shared electrons more strongly than the pull of either atom above it.
About equal to the metals above it, because they all sit in the same group.
Impossible to predict without a measurement.
PTB-040 · medium · application · seq 13 · seed:U3-G3/pool[30] (PTB-040 gateItems[0], the specNotes-sanctioned noble-gas keyed trap; must_freshen_instance + freshness_same_lesson) — freshened WHOLESALE Period 2 -> Period 5: F->I (key), Ne->Xe (trap, feedback verbatim element-free), O->Sb (stopped-short, 'one element' count dropped — Te sits between and is 040-seen), Li->Rb (inverted, feedback verbatim modulo instance); RESOLVES stage 1's flagged F/Ne partial rule-content adjudication WITHOUT adjudicating (clean full freshen; gate_config stays empty; David flag downgraded to FYI-resolved); explanation keeps the seed shape, fluorine-record tail dropped (fluorine-only fact); real data: I 2.66 = Period 5's highest EN, Rb 0.82 its lowest, Sb 2.05 < I; leftover sweep clean · mcq4
Across the whole of Period 5, which element has the highest electronegativity?
Iodine KEY
Xenon
Antimony
Rubidium
PTB-042 · medium · application · seq 14 · seed:U3-G3/pool[38] (= PTB-042 gateItems, James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation; stage-1 flags: freshness_scope_article WARN only (B/N fresh for 042; boron/nitrogen sit in 030/031/032/038/040/042-sibling seeds and specs — no article states the B-vs-N metallic comparison) · mcq4
Boron and nitrogen both sit in Period 2, and nitrogen is the less metallic of the two. What causes the difference?
Across a period the nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly and are harder to give away. KEY
Nitrogen is a gas, and gases can never show metal behavior.
Nitrogen's atoms are larger than boron's, and larger atoms hold every electron more tightly, so their outer electrons are too firmly held to be given away in reactions.
Nitrogen has fewer electron shells than boron.
PTB-043 · medium · application · seq 15 · seed:U3-G3/pool[41] (= PTB-043 gateItems[2], James) — FRESHENED per placement flags (the retired-Z87 pick/cesium/lithium all 043-seen) + 2026-09-07 RECOVERY SWEEP (widened course instance rule): GROUP SWAP re-landed on Group 15 named via members antimony + bismuth (both 043-clean, seq-15 disjoint: A Sr+Mg / B B+Tl / D Se+Te / E element-free); the one-row-short escape-hatch foil recast onto the class-studied framing (same misconception class; the retired instance's real-world scarcity claim does not carry); 'seven outer electrons' -> 'five outer electrons' (Group 15); top-element foil stays positionally unnamed; one-row-short, top-inverted, and equal-outer-count foil families preserved. — 2026-09-08 SOL WAVE 4 (deterministic class sweep of the B#15/D#10 sol-major class: bismuth is NOT at Group 15's very bottom — moscovium sits below it): the superlative is now scoped to the run 'from the group's top row down to bismuth', which bismuth truly bottoms; all three foil families preserved · mcq4
Antimony sits low in its group, and bismuth sits in the row just below it. Considering the group's members from its top row down to bismuth, which would you predict to be the most metallic, and why?
Bismuth, the lowest of that run — down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly and are easier to give away. KEY
Antimony, because it is the most metallic member of the group that the class has actually studied, and a trend can never say anything about an element no lesson has covered.
The element at the very top of the group, because the trend puts the strongest behavior first.
The group's members are all equally metallic, because each has five outer electrons.
PTB-048 · medium · application · seq 16 · seed:U3-G3/pool[56] (= PTB-048 gateItems[2], James) STRUCTURE-KEPT, instance freshened wholesale per must_freshen_instance + freshness_same_lesson (Cl/Br/I EN 3.16/2.96/2.66 = 048's own gate/extraNotes set): Group 4 boiling points, rising — Ti 3287 / Zr blank(highlighted) / Hf 4603 in the reference-TABLE blind-family figure; neighbor values live only in the figure (seed-56/R1 discipline); key = the bounded range; halfway foil exactly 3945 (exact division), measured 4409 is not the halfway point; outside-foil feedbacks use the fluency-2 rising-set wording classes — 2026-09-08 BLIND WAVE 3 (r1: interpolation unanswerable without a stated trend): stem now states the steady rise, the same premise the sibling A#16/E#16 stems already carry; key/foils unchanged (the bounding-vs-midpoint discrimination is untouched) · mcq4
The table shows boiling points for three Group 4 metals, with zirconium's entry blank between titanium's and hafnium's. The group's boiling points rise steadily down the column. What can you predict about zirconium's boiling point?
FIGURE (data-table · stimulus) — title: "Boiling points down Group 4" · columns: ["Element", "Boiling point (°C)"] · rows: [["Ti", "3287"], ["Zr", "? (highlighted blank)"], ["Hf", "4603"]] · style: "column table, blank cell highlighted"
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It lies between 3287 and 4603 °C. KEY
It is above 4603 °C.
It is below 3287 °C.
It is exactly 3945 °C, the halfway point.
PTB-044 · hard · transfer · seq 17 · seed:U3-G3.pool[43] (= PTB-044 gateItems, James) — FRESHENED per placement flags (must_freshen_instance + freshness_same_lesson: 'Group 16' + the oxygen-to-tellurium run are 044's own): group label and every element mention freshened AWAY to the generic 'group of nonmetals' surface (rule line 4's own register); key + d2 + d3 texts and d1/d3 feedback carried verbatim, d1 text and d2 feedback element-swept · mcq4
Reactivity falls steadily from the top of a group of nonmetals to the bottom. What causes the decrease?
A nonmetal atom reacts by pulling in extra electrons, and it reacts more easily when that pull is stronger — down the group the outer shell sits farther from the nucleus, so the pull on an incoming electron is weaker. KEY
The nuclear charge decreases steadily from the top of the group to the bottom, so the atoms lower in the group lose their grip on incoming electrons, and with the weaker grip the reactions run more and more slowly.
Atoms lower in the group have fewer outer electrons and so react less.
Bigger atoms move more slowly, so they collide with other substances less often.
PTB-047 · hard · transfer · seq 18 · seed:U3-G3/pool[52] (= PTB-047 gateItems[1], James) — VERBATIM: stem, key, all three distractors, misconceptions, explanation, figureSpec (blindDescription added — authoring-side interim, see flags); stage-1 flags [] (zero); stem/options element-free; feedback carries the radius panel's own drawn labels/values (Li/Na/K, 186/99 — recorded expected observation) · mcq4
A student claims that in each period, the largest atom comes at the period's end. What does the atomic-radius graph show?
FIGURE (data-graph · stimulus) — title: "Atomic radius against atomic number (elements 3-20, noble gases left out)" · xAxis: "atomic number" · yAxis: "atomic radius (pm)" · points: "Li 152, Be 112, B 85, C 77, N 75, O 73, F 72, Na 186, Mg 160, Al 143, Si 118, P 110, S 104, Cl 99, K 227, Ca 197" · annotations: ["element symbols labeled at peaks", "in-figure note: noble gases measured differently — left out"] · style: "line plot, points joined in atomic-number order" · blindDescription: "A line graph plotting one point per element, joined in atomic-number order, with an in-figure note that the noble gases are measured differently and left ou…
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  "yAxis": "atomic radius (pm)",
  "points": "Li 152, Be 112, B 85, C 77, N 75, O 73, F 72, Na 186, Mg 160, Al 143, Si 118, P 110, S 104, Cl 99, K 227, Ca 197",
  "annotations": [
   "element symbols labeled at peaks",
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  "style": "line plot, points joined in atomic-number order",
  "blindDescription": "A line graph plotting one point per element, joined in atomic-number order, with an in-figure note that the noble gases are measured differently and left out. The curve starts at a tall labeled peak, falls step by step to the end of its row, jumps up to a taller labeled peak and falls again, then jumps to the tallest labeled peak and begins to fall once more before the plotted range ends — the peak symbols read Li, Na, and K. The horizontal axis reads atomic number; the vertical axis reads atomic radius in picometers."
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The opposite — each period's largest atom is the Group 1 metal that starts it, and the values fall across the period. KEY
The claim is right — the plotted values climb steadily across each period and reach their peak at the period's final element.
The largest atom sits in the middle of each period.
Every atom in a period has about the same radius.
PTB-049 · hard · transfer · seq 19 · seed:U3-G3/pool[57] (= PTB-049 gateItems[0], James) STRUCTURE-KEPT with the mandated must_freshen_instance + freshness_same_lesson applied: the seed's same-lesson hits are the NUMBERS (269, 152, and 'Group 18''s 18 — scan-confirmed); freshened to noble-gas MELTING points Ne -249 / Ar -189 / Kr -157 °C (real, integer style; the only real all-negative group ladder outside 049's seen halogens), 'Group 18' -> 'the noble-gas group' (removes the same-lesson 18 AND one pre-recorded positional-vocabulary adjudication candidate), helium dropped (no melting point at ordinary pressure), xenon deliberately excluded (13C same-form repeat + the 112-token cross-scope WARN both die with it); property moves boiling->melting, resolving row 4's WATCH 2 (4C boiling-point form-C repeat); sign-discipline case, option/feedback/explanation texts carried with values swapped and four->three; leftover sweep clean (zero boiling/269/246/186/152/18 tokens) · mcq4
Claim: 'melting point increases down the noble-gas group.' The table lists three noble gases' melting points in order down the group. Do the data support the claim?
FIGURE (data-table · stimulus) — title: "Claim: melting point increases down the noble-gas group" · columns: ["Element", "Melting point (°C)"] · rows: [["Ne", "-249"], ["Ar", "-189"], ["Kr", "-157"]] · style: "column table with the claim as a caption band"
raw spec
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  "title": "Claim: melting point increases down the noble-gas group",
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Yes — every step rises toward zero, from -249 &deg;C up to -157 &deg;C, so every value supports the claim. KEY
No — all three values are negative, so the melting points cannot be increasing.
No — the values decrease, because 249 is bigger than 157.
The data are mixed — some steps rise toward zero while others fall further below it, so no single direction holds.
PTB-045 · hard · transfer · seq 20 · authored (which-family critique of the universal bottom-most-reactive rule — element-free; the blueprint-mandated authored cross-family variant replacing the spared single-family pool[45]; foil c = right-pick-wrong-reason anti-cue with the nonmetal mechanism swapped onto metals, pool[42] right-conclusion-wrong-reason class; foil d = pool[44]'s substantive position-says-nothing escape hatch, recorded watch class, not V-T5 NOTA) — 2026-09-08 SOL WAVE 4 (sol loop-1 major: with only the family solicited, the key and the right-family-wrong-reason foil both answered 'Metals only'): stem now solicits family AND reason (the B#15 'and why?' construction), making each option a unitary claim; the designed anti-cue foil states its wrong mechanism directly · mcq4
A student writes this rule in their notes: 'In every group of the periodic table, the most reactive element sits at the bottom.' For which family of elements is the student's rule correct, and why?
Metals only — metal reactivity grows down a group, while nonmetal reactivity is greatest at the top, so the rule fails for nonmetal columns. KEY
Both families — reactivity always increases toward the bottom of any group, so every column's most reactive element sits at the bottom.
Metals only — because a metal atom low in its group pulls incoming electrons harder than any atom above it.
Neither family — an element's position within its group says nothing about how reactive it is.
PTB-050 · medium · application · seq 21 · authored (blueprint FRQ case: rising-period table under 4 — demo-2's class moved to a fresh period); case = ELECTRONEGATIVITY across Period 5, scale separating it from ionization energy, direction separating it from radius · frq
A spreadsheet recovered from a crashed lab computer lost its column headers. The surviving sheet lists three Period 5 elements — indium, tin, and tellurium, in their left-to-right order across the period — beside the values shown in the table.
FIGURE (data-table · stimulus) — title: "Property: ______ (header lost)" · columns: ["Element", "Value"] · rows: [["In", "1.78"], ["Sn", "1.96"], ["Te", "2.1"]] · style: "torn-label table, Period 5 left-to-right order"
raw spec
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A spreadsheet recovered from a crashed lab computer lost its column headers. The surviving sheet lists three Period 5 elements — indium, tin, and tellurium, in their left-to-right order across the period — beside the values shown in the table. (a) Name the property the sheet most likely records. Justify your answer using BOTH the direction of the values along the row and the size of the values. (b) A classmate offers two other candidates: ionization energy and atomic radius. Rule out each of the two, citing for each one the cue that eliminates it. (c) A fourth Period 5 element sits between tin and tellurium in the row, but its entry was lost with the header. Assuming the values keep changing steadily along the row, state the RANGE in which its value should fall, and justify the range.
Part a. Name the property the sheet most likely records. Justify your answer using BOTH the direction of the values along the row and the size of the values.
Model: Read the elements and their order first: indium, tin, and tellurium run left to right across Period 5. Read the direction next: every value rises. Match the direction against the trends: rising across a period fits electronegativity, ionization energy, and atomic mass — while atomic radius falls across a period, so radius is out on direction. Check the size of the numbers: every value sits under 4 — exactly electronegativity's roughly 0.7-to-4 scale. Ionization energies are hundreds of kJ/mol, and these elements' atomic masses run above a hundred — nothing like values under 4. Rising across the period, on a scale that tops out near 4 — the lost header most likely said electronegativity. [Answer: electronegativity; also accepted: the pull on shared electrons (electronegativity)]
Part b. A classmate offers two other candidates: ionization energy and atomic radius. Rule out each of the two, citing for each one the cue that eliminates it.
Model: Ionization energy matches the direction — it generally rises across a period — so the scale must decide: ionization energies are hundreds of kJ/mol, and nothing here is above 4. Ionization energy is out on size. Atomic radius is out on direction: radius FALLS across a period, and these values rise. Its scale fails too — radii sit near a hundred picometers, not under 4. So one candidate falls to the scale cue and the other to the direction cue. [Answer: ionization energy fits the rising direction but fails the scale (hundreds of kJ/mol, not values under 4); atomic radius fails the direction (it falls across a period while these values rise); also accepted: IE out on size, radius out on direction (radius also fails on size — near a hundred picometers)]
Part c. A fourth Period 5 element sits between tin and tellurium in the row, but its entry was lost with the header. Assuming the values keep changing steadily along the row, state the RANGE in which its value should fall, and justify the range.
Model: Along a steady run, an element's value is bracketed by the values of its two neighbors in the row. The missing element sits between tin at 1.96 and tellurium at 2.1. So its value should fall between 1.96 and 2.1 — the neighbors give a RANGE, not an exact number, and nothing in the trend justifies naming the exact midpoint. [Answer: between 1.96 and 2.1; also accepted: greater than 1.96 and less than 2.1 | 1.96 to 2.1, stated as a bounding range rather than a single predicted number]
Full model answer. (a) Read the elements and their order first: indium, tin, and tellurium run left to right across Period 5. Read the direction next: every value rises. Match the direction against the trends: rising across a period fits electronegativity, ionization energy, and atomic mass — while atomic radius falls across a period, so radius is out on direction. Check the size of the numbers: every value sits under 4 — exactly electronegativity's roughly 0.7-to-4 scale. Ionization energies are hundreds of kJ/mol, and these elements' atomic masses run above a hundred — nothing like values under 4. Rising across the period, on a scale that tops out near 4 — the lost header most likely said electronegativity. [Answer: electronegativity; also accepted: the pull on shared electrons (electronegativity)] (b) Ionization energy matches the direction — it generally rises across a period — so the scale must decide: ionization energies are hundreds of kJ/mol, and nothing here is above 4. Ionization energy is out on size. Atomic radius is out on direction: radius FALLS across a period, and these values rise. Its scale fails too — radii sit near a hundred picometers, not under 4. So one candidate falls to the scale cue and the other to the direction cue. [Answer: ionization energy fits the rising direction but fails the scale (hundreds of kJ/mol, not values under 4); atomic radius fails the direction (it falls across a period while these values rise); also accepted: IE out on size, radius out on direction (radius also fails on size — near a hundred picometers)] (c) Along a steady run, an element's value is bracketed by the values of its two neighbors in the row. The missing element sits between tin at 1.96 and tellurium at 2.1. So its value should fall between 1.96 and 2.1 — the neighbors give a RANGE, not an exact number, and nothing in the trend justifies naming the exact midpoint. [Answer: between 1.96 and 2.1; also accepted: greater than 1.96 and less than 2.1 | 1.96 to 2.1, stated as a bounding range rather than a single predicted number]

Form D

PTB-033 · easy · recall · seq 1 · authored (name-origin facet, rule line 3; element-free; key = the taught rule sentence per verbatim-rule doctrine; distractor classes: electron-misnamed-as-ion / ion-as-precondition (inverts rule line 4) / nucleus-changed (shared with A's nucleus-untouched class, 2 forms)) · mcq4
The cost of removing one electron from an atom is named the atom's ionization energy. What makes this name fit?
Removing the electron turns the atom into an ion. KEY
The electron that leaves is itself the ion that the name points to.
Only an atom that is already an ion has an ionization energy.
The removal turns the nucleus itself into an ion.
PTB-037 · easy · recall · seq 2 · authored (fresh definitional facet, element-free and value-free: rule line 5's taught consequence — shared electrons are pulled closer to the stronger puller — inverted into an observation -> number inference; stem gram 'the shared electrons are pulled closer to' is rule-line-5 verbatim, rule-gram whitelist class; foils = inverted scale / sharing-means-equal / no-connection denial, the denial foil recorded in the escape-hatch blind-review watch class) · mcq4
Two atoms share electrons, and the shared electrons are pulled closer to one of the two atoms. What does that tell you about the two elements' electronegativity numbers?
The element whose atom the shared electrons sit closer to has the bigger electronegativity number. KEY
The element whose atom the shared electrons sit closer to has the smaller electronegativity number.
The two numbers must be equal — atoms can only share electrons when their pulls match.
It tells you nothing — where shared electrons sit is not connected to the electronegativity numbers.
PTB-041 · easy · recall · seq 3 · authored (define-the-term facet — FL0's taught class flipped definition->term, stem rephrased away from FL0's student-seen wording; element-free; stem + keyExplanation grams ride rule lines 1-3 per the A3 rule-gram whitelist class; foils = FL0's taught surface-property trio with misconceptions in FL0's register, fluency non-stem whitelist sources) · mcq4
A chemistry handbook rates every element on how strongly it shows metal behavior, from very strongly down to barely at all. Which property is the handbook rating?
The element's metallic character KEY
The element's density
The element's shininess
The element's magnetism
PTB-046 · easy · application · seq 4 · authored (fresh variant per the blueprint seq-4 contract: plain numeric rising-down-group read, property rotation to density; Group 11 metals with the COURSE'S OWN established density values from the U01-G3 reference table — Cu 8.9, Ag 10.5, Au 19.3 g/cm³, real and strictly monotonic; distractor slots = lesson-canonical backwards / turn / roughly-constant set, the exact fluency-2 class trio) · mcq4
The table lists the densities of the three Group 11 metals in order from copper at the top of the group down to gold. What trend does the table show?
FIGURE (data-table · stimulus) — title: "Densities of the Group 11 metals" · columns: ["Element", "Density (g/cm³)"] · rows: [["Cu", "8.9"], ["Ag", "10.5"], ["Au", "19.3"]] · style: "plain data table, no annotations"
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  "columns": [
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Density increases from top to bottom down the group. KEY
Density decreases from top to bottom down the group.
Density increases and then decreases down the group.
Density stays roughly constant down the group.
PTB-030 · medium · application · seq 5 · authored (fresh instance per row; WE0's modeled ask — 'Which element has the smaller atoms, and why?' — on a fresh Period-4 main-group surface) · mcq4
Gallium and arsenic sit in Period 4, arsenic farther right. Which element has the smaller atoms, and why?
Arsenic — its greater nuclear charge pulls the same-shell outer electrons in more strongly. KEY
Gallium — atomic radius decreases toward the left of a period, so the atom with fewer protons is the smaller one.
Neither — both atoms' outer electrons share the fourth shell, so the two atoms are the same size.
Arsenic — its outer electrons sit in a shell closer to the nucleus than gallium's.
PTB-031 · medium · application · seq 6 · authored (grip-corollary facet — rule line 2's 'held more weakly' tail as the tested claim; element-free; distractor classes: proton-count-wins (shared with C's d3, 2 forms), exact-cancellation standoff (fresh — resolved by the taught account, never weighed quantitatively per extraNotes), right-direction-wrong-reason via a shrinking valence count) · mcq4
Going down any group of the periodic table, atoms get larger with each row. What happens to each atom's hold on its outer electrons, and why?
The hold weakens — the outer electrons sit farther from the nucleus with each added shell. KEY
The hold strengthens — each row down adds protons to the nucleus, and more protons always grip the outer electrons more tightly.
The hold stays the same — the extra protons' stronger pull exactly cancels the extra distance.
The hold weakens — but only because atoms lower in a group keep fewer outer electrons, leaving less for the nucleus to hold.
PTB-032 · medium · application · seq 7 · authored (asked-order-flip facet: same-period rank asked LARGEST first — the direction-discipline class the gate rehearses on IE at seq 10; canonical rank option architecture per the lesson's extraNotes; instance Sc/Ti/V — three adjacent Period-4 cells, corpus-clean and unreserved, taken because the seq-7 period space is otherwise exhausted; real radii monotonic in every dataset, deliberately not extended past vanadium) · mcq4
The periodic-table snippet highlights scandium, titanium, and vanadium. Rank them from largest to smallest atomic radius.
FIGURE (periodic-table-snippet · stimulus) — highlightedCells: [{"symbol": "Sc", "period": 4, "group": 3}, {"symbol": "Ti", "period": 4, "group": 4}, {"symbol": "V", "period": 4, "group": 5}] · context: "full table outline with only the three highlighted cells carrying symbols" · style: "clean deterministic SVG table outline; highlighted cells share one color; no other symbols printed; no trend arrows" · blindDescription: "A periodic-table outline with exactly three highlighted cells, side by side in one row toward the left-middle of the table, in immediately adjacent columns,…
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Largest to smallest: scandium, titanium, vanadium. KEY
Largest to smallest: vanadium, titanium, scandium.
All three have the same atomic radius, because they sit in the same period.
They cannot be ranked without measured values.
PTB-034 · medium · application · seq 8 · authored (position-inference facet — reverse trend read, price -> period position; anonymous elements X/Z, element-free; key quotes the rule-line-2 direction sentence verbatim (whitelisted, D3 hedge kept) + a novel inference tail; distractor classes: shell-count right-pick-wrong-reason / price-direction inversion / escape-hatch no-placement (recorded watch class)) — 2026-09-08 SOL WAVE 4 (sol loop-1 major: 'far less' did not exclude the taught one-step IE dips, so the escape foil stayed defensible): the gap is now 'less than half' (no taught dip approaches that depth), the escape foil overclaims cleanly ('nothing at all'), and the explanation states why the dip case is excluded; 'most likely' ask retained — 2026-09-08 SOL WAVE 5 (sol loop-2 major, same class as the C#20 loop-1 fail: with only the element solicited, the key and the right-element-wrong-reason foil both answered X): stem now solicits element AND reason (the B#15/C#20 construction sol passed), making each option a unitary claim — 2026-09-08 SOL WAVE 6 (sol loop-3 major: the strong-grip distractor's own chain pointed at X, not Z — internally incoherent): rewritten as a coherent-but-wrong chain that lands on Z (strong hold -> left end; the real trend puts strong holds on the right); feedback names the full error · mcq4
Elements X and Z share a period. Pulling one electron off an X atom costs less than half the energy of pulling one off a Z atom. Which element most likely sits farther left in the period, and why?
X — ionization energy generally increases from left to right across a period, so the far cheaper removal sits toward the left. KEY
X — but only because atoms near a period's left end hold their outer electrons in an earlier, smaller shell.
Z — the harder an atom holds its outer electrons, the farther left it sits in its row, and Z's high removal price shows the stronger hold.
No placement can be made — ionization energies say nothing at all about where elements sit in a period.
PTB-035 · medium · application · seq 9 · authored (FL2's which-is-harder direction-discipline shape, modeled-then-tested; ask rotated to MORE energy so the key is the TOP element, against B's less-energy ask; stem rephrased away from FL2's student-seen wording; fresh pair germanium/tin — germanium zero-hit in all 21 scope corpora, tin one non-ionization WARN (043); Sn/Pb and Group-11 pairs rejected on real-IE grounds (Pb 716 > Sn 709, Au 890 > Cu 745 — would invert the taught trend); no group number printed) · mcq4
Germanium and tin share a group, tin one row lower. From which of the two atoms does removing one electron take more energy?
Germanium — its outer electrons sit closer in and are held more tightly. KEY
Tin — the atom with more electron shells grips its outermost electron more tightly.
Both take the same energy, because germanium and tin each have four outer electrons.
It cannot be predicted from their positions.
PTB-036 · medium · application · seq 10 · authored (fresh instance per row; FL2's modeled-then-tested single-pick shape — 'Which of the three has the highest ionization energy?' — on a fresh Group-14 column; group-number label deliberately avoided to dodge a fresh >12 positional-vocabulary scan hit) — 2026-09-08 SOL WAVE 4 (sol loop-1 major: flerovium lies below lead in Group 14): absolute claim -> 'the lowest of the three' (sol's own wording); key and foils untouched · mcq4
Carbon, silicon, and lead all sit in the same group — carbon highest in the column, silicon just below it, and lead the lowest of the three. Which of the three has the highest ionization energy?
Carbon KEY
Lead
Silicon
All three are the same
PTB-038 · medium · application · seq 11 · authored (fresh facet: element-free INVERSE position inference — measured pull difference -> who sits farther right; anonymous elements X/Z per the pool-10 'Atom A/Atom B' register; foils = metal-grip-left (pool 25-b class), noble-gas overshoot (038 FL2's argon-foil class — killed by the taught exclusion, not by the stem), position-says-nothing (FL0-d cannot-tell class)) · mcq4
Two elements, X and Z, sit in the same period. Measurements show that X's atoms pull shared electrons more strongly than Z's atoms do. What do the measurements tell you about where the two elements sit in the row?
X sits farther right in the row than Z does. KEY
X sits at the far left of the row, among the metals, because metal atoms hold every electron — their own and shared ones — most tightly.
X is the row's noble gas, sitting at the very end, because the strongest pull of all belongs to the rightmost element.
Nothing — where an element sits in its period is not connected to how strongly its atoms pull on shared electrons.
PTB-039 · medium · application · seq 12 · authored (forward statement-compare facet — modeled by fluency-1/fluency-3, stem recast away from their shared stem clause; indium/thallium = zero-hit fresh pair across all 21 corpora AND all 63 pool seeds; main-group per the row-5 d-block precedent; real EN In 1.78 > Tl 1.62 agrees with the taught direction, values not printed; group identified positionally — no >12 label introduced; key mirrors fluency-3's whitelisted misconception gram; foils = inverted-group-direction / electrons-do-the-pulling / valence-count-equal, each a taught 039 class; two 'Thallium's atoms' openers = anti-cue) · mcq4
Indium and thallium sit in the same group of the periodic table, thallium one row below indium. Which statement correctly compares how strongly their atoms pull shared electrons?
Indium's atoms pull shared electrons more strongly, because thallium's outer electrons sit a shell farther from the nucleus, where they are held more weakly. KEY
Thallium's atoms pull shared electrons more strongly, because electronegativity grows from the top of a group to the bottom.
Thallium's atoms pull shared electrons more strongly, because they carry more electrons in total, and the more electrons an atom carries, the more pulling power it can put on a shared pair.
The two pull equally, because both have three outer electrons.
PTB-040 · medium · application · seq 13 · authored (asked-order group-rank facet: highest to lowest down an UNNAMED group — no new >12 group label; N/As/Bi all 040-fresh, real EN strictly monotonic 3.04 > 2.18 > 2.02, values not printed; end rows stated in-stem with wording gram-disjoint from placed seed pool[40]; foils = reversed-asked-order / lower-pair swap / class-refusal (TRUE premise nonmetal-metalloid-metal, substantive escape-hatch watch class); no mechanism re-derivation; bismuth bare position instance, binding-rule clean) · mcq4
Nitrogen, arsenic, and bismuth all sit in the same group of the periodic table — nitrogen in the top row of the three, bismuth in the bottom row. Rank them from highest to lowest electronegativity.
Nitrogen, arsenic, bismuth KEY
Bismuth, arsenic, nitrogen
Nitrogen, bismuth, arsenic
They cannot be ranked, because the group mixes a nonmetal, a metalloid, and a metal
PTB-042 · medium · application · seq 14 · authored (FL2's modeled-then-tested shape — 'Which element's atoms give away outer electrons more easily?' — with all three FL2 foil families kept and instances swapped; fresh nonmetal pair P/S in Period 3, own-lesson clean for 042; pair kept off Group 1 so the Group-1-fence foil stays coherent, mirroring FL2's own Be/O) — 2026-09-08 BLIND WAVE 3 (r1 F2 real-chemistry ambiguity: sulfur's measured first IE sits BELOW phosphorus's — the half-filled 3p³ exception — so the taught trend and measurement disagreed on the P/S pair): pair -> S/Cl (S ≈1000 < Cl ≈1251 kJ/mol; taught trend and measurement agree; no subshell exception between them); FL2 shape and all three foil families carried — 2026-09-08 WAVE 3b: S/Cl rerouted to Al/S after the validator proved chlorine sits in PTB-042's own seen set (own-lesson material) and on form A (A#2): aluminum-vs-sulfur keeps the taught across-period direction with measured first IEs agreeing (Al 578 < S 1000 kJ/mol — no half-filled-subshell exception in the comparison), preserves the r1 F2 fix, and keeps both elements off Group 1 for the fence foil — 2026-09-08 WAVE 3c (final): S/Cl and Al/S reroutes both hit PTB-042's own seen set (validator-proven), so the stage-2-proven-clean P/S pair is restored and the QUESTION recast to the course-defined construct ('stronger metallic character', sibling-row register) — r1's own suggested remedy; the measured-IE half-filled-subshell exception (S 1000 < P 1012 kJ/mol) no longer bears on the key because the item no longer asks about electron removal; foil families kept (inverted-direction / shared-period-equal / Group-1-fence recast to the same construct) · mcq4
Sulfur sits just right of phosphorus in Period 3 of the table. Which element shows the stronger metallic character?
Phosphorus KEY
Sulfur
Both equally, because both are Period 3 elements
Neither — metallic character belongs only to Group 1 elements
PTB-043 · medium · application · seq 15 · authored (FL2's which-shows-stronger pick shape, modeled-then-tested; ask ROTATED to WEAKER metal behavior so the key is the TOP element, selenium — asked-order discipline against A/B/C's lower-element keys; fresh pair selenium/tellurium = the last living same-group pair (gallium dead 5D/10B, P/S dead at adjacent 14D, Group 14 043-seen, Group 2 blocked); both untracked; real IE Se 941 > Te 869 kJ/mol, Se nonmetal / Te metalloid — taught direction factually clean, values not printed; foil wording varied off 9D's same-form variants and 14E's 'equally strong' gram) · mcq4
Selenium and tellurium share a group, tellurium one row lower. Which of the two elements shows the weaker metal behavior?
Selenium KEY
Tellurium — each added shell tightens an atom's hold on its outer electrons.
Both show the same strength of metal behavior, because they sit in the same group.
It cannot be judged from their positions.
PTB-048 · medium · application · seq 16 · authored (fresh variant in the lesson's fluency register — the fluency-1/2/3 blank-table class): Group 10 atomic masses, rising — Ni 58.7 / Pd blank(highlighted) / Pt 195.1 in the reference-TABLE blind-family figure; halfway foil exactly 126.9 ((58.7+195.1)/2, exact division); measured 106.4 is nowhere near halfway — the range-not-average teach with teeth; family chosen after dodging C/Si/Ge (carbon 12.0 + boron 10.8 sit in 046's article mass table; carbon/silicon already on sibling form-D rows 10/14), G13 (gallium on 5D), G4 (titanium on 7D), G11 (row 4D), and G18 masses (argon's mass = 049's taught reversal fact) — 2026-09-08 BLIND WAVE 3 (advisory, same class as C#16 — deterministic class sweep): stem states the steady rise (A#16/E#16 premise parity) · mcq4
The table shows atomic masses for three Group 10 metals, with palladium's entry blank between nickel's and platinum's. The group's atomic masses rise steadily down the column. What can you predict about palladium's atomic mass?
FIGURE (data-table · stimulus) — title: "Atomic masses down Group 10" · columns: ["Element", "Atomic mass"] · rows: [["Ni", "58.7"], ["Pd", "? (highlighted blank)"], ["Pt", "195.1"]] · style: "column table, blank cell highlighted"
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It lies between 58.7 and 195.1. KEY
It is above 195.1.
It is below 58.7.
It is exactly 126.9, the halfway point.
PTB-044 · hard · transfer · seq 17 · authored (FL2's bottom-prediction shape — the lesson's own canonized transfer class per extraNotes — with the bottom member ANONYMIZED as nonmetal X in the 2026-09-07 RECOVERY SWEEP: every named halogen/Group-16 nonmetal is 044-seen and seq 17 is saturated with the Group-15 trio on forms A/B/E; the seed pool-44 key 'Below tellurium' denotes exactly this bottom slot). · mcq4
Nonmetal X is the lowest-sitting member of its group, and every member of the group is a nonmetal. Based on the group direction, what does the trend predict for X's reactivity compared with the rest of the group?
The least reactive of the group KEY
The most reactive of the group
About the same as the elements above it
Impossible to say without an experiment
PTB-047 · hard · transfer · seq 18 · authored (IE-graph extension to the complementary landmark — xenon, Z=54, noble gas -> peak, rule line 2; pool-53's canonical extension architecture with every shared-slot wording RESTATED (seeds keep the sentence, authored forms restate — row07 discipline); xenon = the only clean noble gas (He/Ne/Ar/Kr 047-seen; the Period-6 noble gas retired by the instance rule); real-data audit: Xe 1170 kJ/mol = Period 5's IE maximum, monotone main-group run, crash after it = cesium — 18D/18A frame the same period boundary on different forms; key height-agnostic) · mcq4
Xenon, atomic number 54, is a noble gas. The ionization-energy graph's repeating pattern continues past the plotted range. Where would xenon's point sit if the graph were extended to reach it?
FIGURE (data-graph · stimulus) — title: "Ionization energy against atomic number (elements 1-20)" · xAxis: "atomic number" · yAxis: "ionization energy (kJ/mol)" · points: "H 1312, He 2372, Li 520, Be 899, B 801, C 1086, N 1402, O 1314, F 1681, Ne 2081, Na 496, Mg 738, Al 578, Si 786, P 1012, S 1000, Cl 1251, Ar 1521, K 419, Ca… · annotations: ["element symbols labeled at peaks and valleys"] · style: "line plot, points joined in atomic-number order" · blindDescription: "A line graph plotting one point per element, joined in atomic-number order across the plotted range. The curve climbs to a sharp labeled peak, drops steeply…
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At a peak — the top of its period's rise KEY
At a crash — the low point that opens a new period
Partway up the rise, well below its period's peak
Nowhere definite — an unplotted element's point cannot be predicted
PTB-049 · hard · transfer · seq 19 · authored (the row's missing CONTRADICTED-AT-EVERY-STEP verdict facet — modeled by the WE's Group-17 radius case and fluency-2's Group-17 boiling-point case; 'the data contradict the claim at every step' = fluency-2 feedbackScaffold wording, A3 class): claim 'boiling point increases down Group 1' vs real Group-1 boiling points Li 1342 / Na 883 / K 759 / Rb 688 / Cs 671 °C — every step falls; Group-1 element NAMES are 049-seen, so every text field is kept ELEMENT-FREE (pool-57's own pattern; elements ride only as table symbols); all five values scan-clean against every scope lesson; no scope lesson states Group-1 boiling points (memory nil, blind watch); 'Group 1' sub-12; foils = direction-blind steady-change / reversed-path bottom-up read (fluency-2's class, element-free) / mixed-data phantom (pool-57's d class, re-worded) · mcq4
Claim: 'boiling point increases down Group 1.' The table records the boiling points of five Group 1 metals in order down the group. Do the data support the claim?
FIGURE (data-table · stimulus) — title: "Claim: boiling point increases down Group 1" · columns: ["Element", "Boiling point (°C)"] · rows: [["Li", "1342"], ["Na", "883"], ["K", "759"], ["Rb", "688"], ["Cs", "671"]] · style: "column table with the claim as a caption band"
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No — every step falls, from 1342 °C down to 671 °C, so the data contradict the claim at every step. KEY
Yes — the values change steadily from row to row, and a steady change is what a trend claim needs.
Yes — read from the bottom of the table up to the top, the values rise from 671 °C to 1342 °C.
The data are mixed — the values both rise and fall on the way down, so no single direction holds.
PTB-045 · hard · transfer · seq 20 · authored (cause facet — why the two directions point opposite ways; key = rule line 2's + rule line 3's reason clauses VERBATIM, the short clauses 045's extraNotes license — the full PTB-043/PTB-044 mechanisms are not restated; foils = size-asymmetry-invented / table-geography-cause / room-not-pull (pool[42]'s taught room class); band note recorded: cause-ask leans application, parity held by the novel cross-family synthesis, 17C precedent) · mcq4
Down a group, metal reactivity grows while nonmetal reactivity fades. Why do the two directions point opposite ways?
A metal reacts by giving away outer electrons, and lower down those electrons are held more weakly — but a nonmetal reacts by pulling in extra electrons, and lower down that pull is weaker. KEY
Metal atoms grow larger down a group while nonmetal atoms instead grow smaller and smaller, so the two families' size trends drag their reactivities in opposite directions.
Metals and nonmetals sit on opposite sides of the periodic table, and a trend that runs one way on the metal side must automatically run the opposite way on the nonmetal side.
Nonmetal atoms near the bottom of a group run out of room for extra electrons, so their reactivity dies away.
PTB-050 · medium · application · seq 21 · authored (blueprint FRQ case: metal reactivity available as a fresh property; fluency-3's observation-log SHAPE moved from Group 1 to Group 2 with fresh phrasing); case = REACTIVITY read from a behavior log — the data's FORM eliminates every numeric property, and the direction confirms the metals' taught trend — 2026-09-08 BLIND WAVE 3 (course-wide classroom-safe instance rule + r1 safety flag: the element below barium is RADIUM — even a hypothetical cold-water test is off-palette): part (c) now asks about the Group 2 metal directly ABOVE calcium (magnesium, unnamed); prediction = TAMER than calcium's, the same trend applied in the inverse direction (and reality agrees: magnesium barely reacts with cold water); parts (a)/(b), rubric weights, and the observation-log figure untouched · frq
A page in an old lab notebook has its title line smeared beyond reading. Below it, a table lists three Group 2 metals — calcium, strontium, and barium, in order down the group — each beside the note the experimenter wrote when a small piece of the metal was dropped into cold water.
FIGURE (data-table · stimulus) — title: "________ (title smeared)" · columns: ["Element", "Recorded behavior"] · rows: [["Ca", "gives off a steady stream of bubbles; the water slowly turns cloudy"], ["Sr", "bubbles rapidly and vigorously"], ["Ba", "reacts violently the moment… · style: "observation log, Group 2 order top to bottom"
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A page in an old lab notebook has its title line smeared beyond reading. Below it, a table lists three Group 2 metals — calcium, strontium, and barium, in order down the group — each beside the note the experimenter wrote when a small piece of the metal was dropped into cold water. (a) Name the property the experimenter was most likely recording. Justify your answer using BOTH the direction of the records down the group and the KIND of data recorded (written observations rather than numbers). (b) A classmate suggests the notebook column might instead record electronegativity or ionization energy. Rule out each of the two, citing for each one a cue that eliminates it. (c) One more Group 2 metal sits directly above calcium, one row higher in the group. If the experimenter had run the same test on that metal, predict how its recorded behavior would compare with calcium's, and justify your prediction.
Part a. Name the property the experimenter was most likely recording. Justify your answer using BOTH the direction of the records down the group and the KIND of data recorded (written observations rather than numbers).
Model: Read the elements and their order first: calcium, strontium, and barium run top to bottom down Group 2. Read the direction next: the recorded behavior grows more violent with every step down — steady bubbling, then vigorous bubbling, then a violent reaction on contact. Check the KIND of data: these are written descriptions of how the metal behaves, not numbers — electronegativity, ionization energy, atomic radius, and atomic mass are all values on numeric scales, so none of them can be a column of observations. Match the direction: for metals, reactivity increases down the group — a metal reacts by giving away outer electrons, and lower down those electrons are held more weakly. Growing violence down Group 2 is exactly that trend. Behavior records, growing more violent down the group — the smeared title most likely said reactivity. [Answer: reactivity; also accepted: how reactive the metal is (metal reactivity) | reactivity with water]
Part b. A classmate suggests the notebook column might instead record electronegativity or ionization energy. Rule out each of the two, citing for each one a cue that eliminates it.
Model: Both candidates are NUMBERS: electronegativity is a value on a scale that runs from about 0.7 to 4, and ionization energy is measured in hundreds of kJ/mol. A column of written observations about fizzing and violent reactions records neither. Both also fail on direction: electronegativity and ionization energy FALL going down a group, while the recorded vigor here GROWS with every step down. So each candidate is eliminated twice over — by the kind of data and by the direction. [Answer: electronegativity is a number on the roughly 0.7-to-4 scale and falls down a group — it is neither a written behavior nor growing downward; ionization energy is a number in hundreds of kJ/mol and also falls down a group — same double mismatch; also accepted: both are numeric properties (0.7-4 scale; hundreds of kJ/mol), and both fall down a group while the recorded vigor grows]
Part c. One more Group 2 metal sits directly above calcium, one row higher in the group. If the experimenter had run the same test on that metal, predict how its recorded behavior would compare with calcium's, and justify your prediction.
Model: For metals, reactivity increases down the group — a metal reacts by giving away outer electrons, and lower down those electrons are held more weakly. The metal above calcium sits one row higher in the group, so its outer electrons are held more tightly and are given away less easily than calcium's. So that metal's recorded behavior should be tamer than calcium's — slower, weaker bubbling, if much visible reaction at all — the trend runs the other way going up the group. [Answer: a tamer reaction than calcium's — the metal above calcium reacts less vigorously, since metal reactivity falls going up the group; also accepted: less vigorous than calcium's (slow or scant bubbling), because metal reactivity decreases going up the group | a weaker/slower reaction than calcium's, because its outer electrons are held more tightly and given away less easily]
Full model answer. (a) Read the elements and their order first: calcium, strontium, and barium run top to bottom down Group 2. Read the direction next: the recorded behavior grows more violent with every step down — steady bubbling, then vigorous bubbling, then a violent reaction on contact. Check the KIND of data: these are written descriptions of how the metal behaves, not numbers — electronegativity, ionization energy, atomic radius, and atomic mass are all values on numeric scales, so none of them can be a column of observations. Match the direction: for metals, reactivity increases down the group — a metal reacts by giving away outer electrons, and lower down those electrons are held more weakly. Growing violence down Group 2 is exactly that trend. Behavior records, growing more violent down the group — the smeared title most likely said reactivity. [Answer: reactivity; also accepted: how reactive the metal is (metal reactivity) | reactivity with water] (b) Both candidates are NUMBERS: electronegativity is a value on a scale that runs from about 0.7 to 4, and ionization energy is measured in hundreds of kJ/mol. A column of written observations about fizzing and violent reactions records neither. Both also fail on direction: electronegativity and ionization energy FALL going down a group, while the recorded vigor here GROWS with every step down. So each candidate is eliminated twice over — by the kind of data and by the direction. [Answer: electronegativity is a number on the roughly 0.7-to-4 scale and falls down a group — it is neither a written behavior nor growing downward; ionization energy is a number in hundreds of kJ/mol and also falls down a group — same double mismatch; also accepted: both are numeric properties (0.7-4 scale; hundreds of kJ/mol), and both fall down a group while the recorded vigor grows] (c) For metals, reactivity increases down the group — a metal reacts by giving away outer electrons, and lower down those electrons are held more weakly. The metal above calcium sits one row higher in the group, so its outer electrons are held more tightly and are given away less easily than calcium's. So that metal's recorded behavior should be tamer than calcium's — slower, weaker bubbling, if much visible reaction at all — the trend runs the other way going up the group. [Answer: a tamer reaction than calcium's — the metal above calcium reacts less vigorously, since metal reactivity falls going up the group; also accepted: less vigorous than calcium's (slow or scant bubbling), because metal reactivity decreases going up the group | a weaker/slower reaction than calcium's, because its outer electrons are held more tightly and given away less easily]

Form E

PTB-033 · easy · recall · seq 1 · authored (name-the-quantity facet — the WE-2/fluency-2 taught class, instance rotated to boron (classroom set; taught instances magnesium/aluminum are 033-seen); foils = sibling quantities: fluency-2's nuclear-charge and atomic-radius classes re-worded + the post-topic-6 electronegativity discrimination) · mcq4
It costs energy to pull one electron off a boron atom. What is this energy's name?
Boron's ionization energy KEY
Boron's electronegativity
Boron's nuclear charge
Boron's atomic radius
PTB-037 · easy · recall · seq 2 · authored (fresh definitional facet, element-free critique: student defines electronegativity as the electron-removal energy — the ionization-energy confusion, fluency-1's lead misconception flipped into the stem; ionization energy is in-scope, PTB-033/seq-1; foils = conflation / valence-count swap / whole-atom-attraction swap, exactly fluency-1's misconception classes in critique form; the quoted wrong definition paraphrases the 033 idea, never a verbatim rule line) · mcq4
A student writes: &quot;An element's electronegativity is the amount of energy needed to remove one electron from its atoms.&quot; What is wrong with the student's statement?
The student described ionization energy — electronegativity measures the pull on electrons shared with another atom. KEY
Nothing is wrong — the removal energy and the pull on shared electrons are the same measurement.
The statement should say that electronegativity counts how many electrons sit in an atom's outer shell.
The statement should say that electronegativity measures how strongly an atom attracts other whole atoms.
PTB-041 · easy · recall · seq 3 · authored (weak-end inference facet — FL2's taught class, stem rephrased gram-disjoint from FL2's student-seen stem; element-free; key rides FL2's key = fluency non-stem A3 whitelist source; foils = FL1's reacting-equals-metallic family, FL2's noble-gas overreach, FL1's all-or-nothing family anchored on rule line 1's strongly/weakly/barely spectrum) · mcq4
During reactions, a certain element's atoms never give up an outer electron — they grip their own electrons firmly and draw in extras from other atoms. What does this behavior say about the element's metallic character?
Its metallic character is weak — the element behaves as a nonmetal. KEY
Its metallic character is strong — drawing in electrons is a way of reacting, and reacting is metal behavior.
The element must be a noble gas, because only noble gases refuse to hand over electrons.
Metallic character cannot be called weak or strong — an element simply is a metal or is not.
PTB-046 · easy · application · seq 4 · authored (fresh variant per the blueprint seq-4 contract: plain numeric falling-down-group read, property rotation to ionization energy; five Group 18 elements with real first ionization energies He 2372 / Ne 2081 / Ar 1521 / Kr 1351 / Xe 1170 kJ/mol, integer style matching the course's IE values; noble gases DO rank on ionization energy — course-local discipline, restated in the explanation; distractor slots = backwards / no-clear-trend / roughly-constant, all lesson-canonical classes) · mcq4
The table lists the ionization energies of five Group 18 elements in order from helium at the top of the group down to xenon. What trend does the table show?
FIGURE (data-table · stimulus) — title: "Ionization energies of five Group 18 elements" · columns: ["Element", "Ionization energy (kJ/mol)"] · rows: [["He", "2372"], ["Ne", "2081"], ["Ar", "1521"], ["Kr", "1351"], ["Xe", "1170"]] · style: "plain data table, no annotations"
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Ionization energy decreases from top to bottom down the group. KEY
Ionization energy increases from top to bottom down the group.
The values show no clear trend.
Ionization energy stays roughly constant down the group.
PTB-030 · medium · application · seq 5 · authored (fresh instance per row; FL2's accounts-for-the-measured-difference shape — modeled-then-tested, sanctioned — on a fresh Period-5 surface; stem wording rephrased away from the student-seen fluency stem) · mcq4
Measurements show that indium's atoms are larger than antimony's, even though the two share Period 5, antimony farther right. Which statement explains the size difference?
Antimony's greater nuclear charge pulls its same-shell outer electrons in more strongly. KEY
Antimony's outer electrons occupy a shell closer to the nucleus than indium's.
Indium's atoms hold more electrons, and more electrons take up more room.
Indium's atoms are larger because metals always have larger atoms than metalloids.
PTB-031 · medium · application · seq 6 · authored (anonymized shell-stated prediction facet — elements J and M, shell counts in words, two rows apart; key leans on fluency-2's scaffold line verbatim (A3 whitelist source); distractor classes: fewer-shells-looser-swell (inverted grip, shared class with A's d2, 2 forms), same-valence-same-size (shared with B's d3, 2 forms), measurement escape hatch (blueprint watch class, not NOTA)) · mcq4
Elements J and M share a group. J's outer electrons occupy the second shell; M sits two rows lower, with its outer electrons in the fourth shell. Which element has the larger atoms?
M — outer electrons in a farther shell sit farther from the nucleus, so M's atoms are the larger ones. KEY
J — atoms with fewer occupied shells hold their electrons more loosely, and loosely held electrons spread into a larger atom.
The two atoms are the same size, because groupmates keep the same number of outer electrons.
It cannot be told from shell positions alone — only a measured radius for each element can decide which is larger.
PTB-032 · medium · application · seq 7 · authored (largest-pick facet on the group axis — fluency-3's pick class rotated from period to group; pick option architecture from pool[6]; instance As/Sb/Bi — main-group 15, corpus-clean, bismuth = allowed bare-position instance used purely positionally, zero banned framings of any kind; real radii monotonic so the steady-growth foil wording stays true; cross-row As watch vs row 17 recorded in the substance ledger) · mcq4
The periodic-table snippet highlights arsenic, antimony, and bismuth. Which element has the largest atomic radius?
FIGURE (periodic-table-snippet · stimulus) — highlightedCells: [{"symbol": "As", "period": 4, "group": 15}, {"symbol": "Sb", "period": 5, "group": 15}, {"symbol": "Bi", "period": 6, "group": 15}] · context: "full table outline with only the three highlighted cells carrying symbols" · style: "clean deterministic SVG table outline; highlighted cells share one color; no other symbols printed; no trend arrows" · blindDescription: "A periodic-table outline with exactly three highlighted cells, all in one column toward the right side of the table, in consecutive rows: the cell labeled A…
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Bismuth KEY
Arsenic
Antimony
All three are the same size.
PTB-034 · medium · application · seq 8 · authored (which-is-generally-higher facet — the fluency-2 taught class rotated to Ba/Bi in Period 6, bismuth farther right, bare positions; stem fronted 'In Period 6, ...' to dodge kept seed 14A's '...in Period 6. Which...' boundary gram; ask reworded off fluency-2's exact stem clause (stems are corpus, never whitelist); foils = taught classes: size-backwards re-worded, same-shell-same-price re-worded, cannot-be-judged escape hatch verbatim from fluency-2 (A3 whitelist source)) · mcq4
In Period 6, bismuth sits farther right than barium. Which of the two elements generally has the higher ionization energy?
Bismuth — its greater nuclear charge pulls its same-shell outer electrons in more strongly. KEY
Barium — its atoms are the larger ones, and a larger atom keeps a stronger hold on its electrons.
The two are equal, because their outer electrons occupy the same shell.
It cannot be judged from their positions.
PTB-035 · medium · application · seq 9 · authored (FL1's given-the-fact-why shape, modeled-then-tested; key = FL1's key verbatim = the MECH-GROUP-HS canonical sentence with the register extension — rule language repeats by doctrine; foils = FL1's three misconception families re-instanced; fresh pair phosphorus/arsenic — arsenic zero-hit in all 21 scope corpora, phosphorus cross-scope WARN only (032/037/039/040, no ionization facts); antimony deliberately avoided (5E claims In/Sb on form E); no group number printed) · mcq4
Phosphorus and arsenic share a group, arsenic one row lower. Why is arsenic's ionization energy lower than phosphorus's?
Because down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly and take less energy to remove. KEY
Because arsenic has more protons, which push the outer electrons away from the atom.
Because across a period the nuclear charge increases while the outer electrons stay in the same shell, so arsenic's outer electrons are pulled inward harder than phosphorus's.
Because arsenic has fewer outer electrons to remove than phosphorus.
PTB-036 · medium · application · seq 10 · authored (fresh instance per row; gate-1's flipped-asked-order discipline moved to a PERIOD set — fresh combination sanctioned by specNotes ('gate 1 flips the asked order') — plus the EN-exclusion-import foil from the specNotes discrimination 'noble gases allowed in IE rankings (only the EN trend excludes them)') · mcq4
Strontium, tin, and xenon all belong to Period 5 — strontium near the left end of the row, tin toward the right side, and xenon at the far right end. Rank them from highest to lowest ionization energy.
Xenon, tin, strontium KEY
Strontium, tin, xenon
Xenon, strontium, tin
Xenon cannot be ranked with the other two, because noble gases are left out of the trend
PTB-038 · medium · application · seq 11 · authored (fresh facet: element-free explain-the-gap cause read — WE0's modeled why-shape on positions only, stem rephrased away from the WE wording; true real-world anchor Period 5 (I 2.66 vs Rb 0.82), neither element named nor any value printed; key = canonical mechanism sentence + shared-electron extension VERBATIM; foils = 038 fluency-2's exact trio, element-free: added-shells import / size-backwards / outer-electron-count) · mcq4
In Period 5, the element just before the noble gas has a much higher electronegativity than the element at the far left end of the row. What makes the right-side element's pull on shared electrons so much stronger?
Because across a period the nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly — and a stronger pull also acts on shared electrons. KEY
Because moving toward the right-hand end of a row adds electron shells, and outer electrons spread across more shells exert a stronger pull on any electrons shared with a neighboring atom.
Because atoms grow larger toward the right-hand end of a row, and the larger the atom, the more strongly it tugs on the electrons it shares with a neighboring atom.
Because atoms toward the right-hand end of a row hold more outer electrons, and every extra outer electron adds its own extra pull on the electrons the atom shares.
PTB-039 · medium · application · seq 12 · authored (why-question on a stated comparison — fluency-2's modeled-then-tested shape, stem rephrased away from fluency-2's wording with no values; calcium/strontium fresh for 039 — Ca WARN 6 corpora / Sr WARN via 048's radius bounding only, no EN content anywhere, memory-answerability nil; real EN Ca 1.00 > Sr 0.95, values not printed; key = fluency-2's key VERBATIM = rule line 4; foil b = fluency-2's period-mechanism distractor VERBATIM; foils c/d = mass-ties-pull and metals-out-of-scale, both taught 039 classes with feedback naming this form's elements) · mcq4
Calcium sits one row above strontium in Group 2, and calcium's atoms pull shared electrons more strongly than strontium's atoms do. Why?
Because down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly — and a weaker hold means a weaker pull on shared electrons. KEY
Because across a period the nuclear charge increases while the outer electrons stay in the same shell, so the outer electrons are pulled in more strongly — and a stronger pull also acts on shared electrons.
Because calcium's atoms are lighter than strontium's, and lighter atoms always grip the electrons they share more tightly.
Because metal atoms as low in a group as strontium stop pulling on shared electrons entirely, so only calcium's atoms pull at all.
PTB-040 · medium · application · seq 13 · authored (group-superlative facet on an UNNAMED group — no new >12 group label; B/Al/Tl with boron the classroom-set pick; real-data honesty: Group 13 EN is non-monotonic below Al (Al 1.61, Tl 1.62), so NO claim orders Al vs Tl — the key asserts only boron-highest (TRUE, 2.04 is the group max) and the equal-pull feedback claims only that the three values differ (TRUE); reasoned options pool[23]-style; foils = inverted group direction / stopped-one-row-short (group-axis mirror of form C's class) / membership-means-equal-pulls (pool[22] family); boron 1E/13E non-adjacent form-E repeat recorded with no-alternative rationale) · mcq4
Boron, aluminum, and thallium all sit in the same group of the periodic table — boron in the top row of the three, thallium in the bottom row. Which of the three has the highest electronegativity?
Boron — electronegativity decreases from the top of a group to the bottom, and boron sits at the top of the three. KEY
Thallium — electronegativity increases from the top of a group to the bottom.
Aluminum — it sits one row below boron, high enough in the group to take the strongest pull.
They are equal — elements that share a group pull shared electrons with the same strength.
PTB-042 · medium · application · seq 14 · authored (claim critique: the metal-label misconception — seed A's d2 family, pool 37 'Both equally, because both are metals' — promoted to the tested claim on the fresh both-metals pair Ba/Tl in Period 6; key applies rule line 3's verbatim tail; foils = metal-label student-right, FL1's mass family with the mass fact kept TRUE, FL0's positions-give-up family verbatim) · mcq4
Barium and thallium both sit in Period 6, barium well to the left of thallium. A student claims that since both elements are metals, they must show equally strong metal behavior. Which response is correct?
The claim is wrong — metallic character fades from left to right along the row, so barium, sitting farther left, shows the stronger metal behavior. KEY
The student is right — once two elements both count as metals, their atoms give away outer electrons equally easily.
Thallium shows the stronger metal behavior, because its atoms are heavier than barium's, and heavier atoms shed their outer electrons more easily.
Neither claim can be checked — metal behavior cannot be judged from positions in the row.
PTB-043 · medium · application · seq 15 · authored (FL1's given-the-fact-why shape, modeled-then-tested; ELEMENT-FREE abstract same-group pair — recorded judgment call: the gate's fresh-instance space is exhausted at this row; James's own element-free register per pool 14 (8A) and pool 10 (1B); key = FL1's key = MECH-GROUP-HS + register extension VERBATIM — rule language repeats across forms by doctrine; foils = FL1's three misconception families element-free) · mcq4
Two elements share a group, and one sits three rows below the other. The lower element is by far the more metallic of the two. Why?
Because down a group each row adds an electron shell, so the outer electrons sit farther from the nucleus and are held more weakly and are easier to give away. KEY
Because across a period the nuclear charge increases while the outer electrons stay in the same shell, so the lower element's outer electrons are pulled in more strongly than its groupmate's.
Because the lower element has more protons, and more protons make an atom more metallic.
Because the lower element's atoms have more outer electrons to give away than its groupmate's atoms.
PTB-048 · medium · application · seq 16 · authored (averaging-critique facet — the lesson's deliberately-keyed anti-target promoted to the key's subject; extraNotes bar interpolation arithmetic and key the 'exactly halfway' distractor against it on every fluency item): Group 5 densities, rising — V 6.11 / Ta 16.65 quoted, student averages the neighbors and claims niobium's density is exactly 11.38 g/cm³ (average stated, not derived — no arithmetic shown); key = the trend pins a RANGE, never an exact number; fresh arithmetic-blame foil (the average IS exactly 11.38, verifiable) plus averaging-accepted and give-up classes; measured 8.57 in the explanation — inside the range, nowhere near the average · mcq4
A student looks up vanadium's density, 6.11 g/cm³, and tantalum's, 16.65 g/cm³. Niobium sits between them in Group 5, and the group's densities rise steadily down the column. The student averages the two neighbors' values and reports that niobium's density must be exactly 11.38 g/cm³. What is wrong with the report?
The steady trend pins niobium's density inside a range, between 6.11 and 16.65 g/cm³ — it does not pick an exact number in that range. KEY
Nothing — when a group's values change steadily, the middle element's value always equals the exact average of its neighbors' values.
The arithmetic is the problem — the average of 6.11 and 16.65 is not 11.38.
It is wrong because a density can never be predicted from an element's position in the table.
PTB-044 · hard · transfer · seq 17 · authored (fresh instance per row; FL0's which-reacts-more-readily ask fused with FL1's discrimination foils — metal-mechanism import, proton-count — plus pool 42's equal-valence family, on the remaining free pair nitrogen/phosphorus; hedged throughout as a trend EXPECTATION) · mcq4
Nitrogen and phosphorus share one group, nitrogen directly above phosphorus, and both react by pulling in extra electrons. Based on the group trend, which statement compares them correctly?
Nitrogen's pull on an incoming electron is the stronger, so nitrogen is expected to react with metals more readily. KEY
Phosphorus holds its outer electrons more loosely, and an atom reacts more easily when its outer electrons are easier to give away — so phosphorus is expected to react with metals more readily.
Phosphorus's atoms hold more protons, and more protons always mean a stronger pull on an incoming electron — so phosphorus is expected to react with metals more readily.
The two are expected to react with metals equally readily, because both atoms have five outer electrons and need three more to fill the shell.
PTB-047 · hard · transfer · seq 18 · authored (radius-graph extension with the LANDMARK FLIP — a Group 1 metal beyond the plotted range -> the peak that OPENS its period; the IE-shape importer — 18C's named misconception — keys the low-point foil; pool-53 architecture, wordings restated; 2026-09-07 RECOVERY SWEEP: the named Period-7 instance replaced by the POSITIONAL 'one Group 1 metal beyond the plotted range' — Rb is 047-seen, Cs sits at 18A (A5), all remaining Group 1 names retired by the instance rule; no peak-height comparison made in any field). · mcq4
One Group 1 metal sits beyond the atomic-radius graph's plotted range. The graph's repeating pattern continues past the plotted elements. Where would that metal's point sit on an extended graph?
FIGURE (data-graph · stimulus) — title: "Atomic radius against atomic number (elements 3-20, noble gases left out)" · xAxis: "atomic number" · yAxis: "atomic radius (pm)" · points: "Li 152, Be 112, B 85, C 77, N 75, O 73, F 72, Na 186, Mg 160, Al 143, Si 118, P 110, S 104, Cl 99, K 227, Ca 197" · annotations: ["element symbols labeled at peaks", "in-figure note: noble gases measured differently — left out"] · style: "line plot, points joined in atomic-number order" · blindDescription: "A line graph plotting one point per element, joined in atomic-number order, with an in-figure note that the noble gases are measured differently and left ou…
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  "title": "Atomic radius against atomic number (elements 3-20, noble gases left out)",
  "xAxis": "atomic number",
  "yAxis": "atomic radius (pm)",
  "points": "Li 152, Be 112, B 85, C 77, N 75, O 73, F 72, Na 186, Mg 160, Al 143, Si 118, P 110, S 104, Cl 99, K 227, Ca 197",
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At a peak — the high point that opens its period KEY
At a low point — the bottom of a long fall
About halfway down its period's fall
No spot can be predicted for an element outside the plotted range
PTB-049 · hard · transfer · seq 19 · authored (the row's missing NOT-FULLY-ONE-BREAK verdict facet — fluency-1's modeled shape: cite the single breaking value, never delete it): claim 'melting point decreases down Group 11' vs real Group-11 melting points Cu 1085 / Ag 962 / Au 1064 °C — a genuine documented break (silver-to-gold rises); copper/silver/gold named in options per the lesson's own style (none 049-seen; copper = single 041 WARN, nil memory; Ag classroom set); values scan-clean everywhere; 'Group 11' sub-12; first-choice Si/Ge/Sn/Pb rejected (tin on 10E+14E, silicon 8 corpora), second-choice Zn/Cd/Hg densities claimed mid-authoring by 16B with the identical values — both recorded; 4D's Cu/Ag/Au DENSITY item is form D (cross-form, disjoint property/values, recorded); foils = skipped-step yes-anyway (A(b) class) / dismissal not-a-group-property (fluency-1's distractor class, misconception feedback VERBATIM) / discard-data set-gold-aside (A(d)'s taught teeth class) · mcq4
Claim: 'melting point decreases down Group 11.' The table shows the melting points of the Group 11 metals, listed from the top of the group down. Do the data support the claim?
FIGURE (data-table · stimulus) — title: "Claim: melting point decreases down Group 11" · columns: ["Element", "Melting point (°C)"] · rows: [["Cu", "1085"], ["Ag", "962"], ["Au", "1064"]] · style: "column table with the claim as a caption band"
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Not fully — the values fall from copper to silver, but silver to gold rises, 962 up to 1064. KEY
Yes — every step in the table falls as you read down the group.
The data cannot test the claim, because melting point is not a group property.
Yes, once gold is set aside as a one-off exception — the remaining values fall cleanly from copper down to silver.
PTB-045 · hard · transfer · seq 20 · authored (decidability facet — bottom-of-group element M with the class withheld; the tested move is rule 1's class-first question, quoted verbatim in the keyExplanation; anonymous 'element M' = the PTB-033 pool[10] anonymous register; two 'No —' openers = right-pick-wrong-reason anti-cue; foils = class-blind-flattening / nonmetal-direction-everywhere (capped with A(c)) / position-never-ranks overcorrection (capped with C(d))) · mcq4
Element M is the lowest member of its group. A classmate claims that this position alone shows M to be the group's most reactive element. Can the claim be checked without knowing whether M is a metal or a nonmetal?
No — the class sets the direction: the lowest spot means most reactive for a metal but least reactive for a nonmetal. KEY
Yes — group trends run the same way for both classes, so the lowest member holds the same rank whether M is a metal or a nonmetal.
Yes — the claim is wrong for any element, because reactivity always fades toward the bottom of a group.
No — and even the class would not settle it, because an element's position never ranks its reactivity.
PTB-050 · medium · application · seq 21 · authored (blueprint FRQ case: falling-group table under 4 — fluency-2's direction-fits-scale-decides class moved from Group 17 to Group 15); case = ELECTRONEGATIVITY down Group 15, ionization energy sharing the direction and failing only on scale · frq
A records office sends over a database export in which the property field's name was replaced by an error code. The export lists three Group 15 elements — arsenic, antimony, and bismuth, in order from arsenic down the group to bismuth — beside the values shown in the table.
FIGURE (data-table · stimulus) — title: "Property: ERR_FIELD_NAME (name lost)" · columns: ["Element", "Value"] · rows: [["As", "2.18"], ["Sb", "2.05"], ["Bi", "2.02"]] · style: "torn-label table, Group 15 order top to bottom"
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A records office sends over a database export in which the property field's name was replaced by an error code. The export lists three Group 15 elements — arsenic, antimony, and bismuth, in order from arsenic down the group to bismuth — beside the values shown in the table. (a) Name the property the export most likely holds. Justify your answer using BOTH the direction of the values down the group and the size of the values. (b) A classmate offers two other candidates: ionization energy (which also falls down a group) and atomic radius. Rule out each of the two, citing for each one the cue that eliminates it. (c) The Group 15 element one row directly ABOVE arsenic was not included in the export. Predict how its value should compare with arsenic's, and justify your prediction.
Part a. Name the property the export most likely holds. Justify your answer using BOTH the direction of the values down the group and the size of the values.
Model: Read the elements and their order first: arsenic, antimony, and bismuth run top to bottom down Group 15. Read the direction next: every value falls. Match the direction against the trends: falling down a group fits ionization energy and electronegativity — while atomic radius, metallic character, and atomic mass all GROW down a group, so those are out on direction. Check the size of the numbers: every value sits under 4, and the only taught property whose values live on that roughly 0.7-to-4 scale is electronegativity — ionization energies are hundreds of kJ/mol. Falling down the group, on a scale that tops out near 4 — the lost field name most likely said electronegativity. [Answer: electronegativity; also accepted: the pull on shared electrons (electronegativity)]
Part b. A classmate offers two other candidates: ionization energy (which also falls down a group) and atomic radius. Rule out each of the two, citing for each one the cue that eliminates it.
Model: Ionization energy matches the direction — it falls down a group, just like these values — so the scale must decide: ionization energies are hundreds of kJ/mol, and nothing here is above 4. Ionization energy is out on size, not direction. Atomic radius is out on direction: radius GROWS down a group as shells are added, and these values fall. Its scale fails too — radii sit near a hundred picometers, not under 4. So the same-direction candidate falls to the scale cue, and the other falls to the direction cue. [Answer: ionization energy fits the falling direction but fails the scale (hundreds of kJ/mol, not values under 4); atomic radius fails the direction (it grows down a group while these values fall); also accepted: IE out on size only, radius out on direction (radius also fails on size — near a hundred picometers)]
Part c. The Group 15 element one row directly ABOVE arsenic was not included in the export. Predict how its value should compare with arsenic's, and justify your prediction.
Model: The values fall going DOWN the group, so going UP the group they rise: each element sits above a lower-valued neighbor. The element one row above arsenic should therefore have a value HIGHER than arsenic's 2.18. It should still sit on the same scale, though — electronegativity's scale tops out near 4, so higher than 2.18 but below about 4. [Answer: higher than 2.18 (and still under the scale's ceiling near 4); also accepted: greater than arsenic's 2.18, since the trend rises going up the group | above 2.18 but on the same under-4 scale]
Full model answer. (a) Read the elements and their order first: arsenic, antimony, and bismuth run top to bottom down Group 15. Read the direction next: every value falls. Match the direction against the trends: falling down a group fits ionization energy and electronegativity — while atomic radius, metallic character, and atomic mass all GROW down a group, so those are out on direction. Check the size of the numbers: every value sits under 4, and the only taught property whose values live on that roughly 0.7-to-4 scale is electronegativity — ionization energies are hundreds of kJ/mol. Falling down the group, on a scale that tops out near 4 — the lost field name most likely said electronegativity. [Answer: electronegativity; also accepted: the pull on shared electrons (electronegativity)] (b) Ionization energy matches the direction — it falls down a group, just like these values — so the scale must decide: ionization energies are hundreds of kJ/mol, and nothing here is above 4. Ionization energy is out on size, not direction. Atomic radius is out on direction: radius GROWS down a group as shells are added, and these values fall. Its scale fails too — radii sit near a hundred picometers, not under 4. So the same-direction candidate falls to the scale cue, and the other falls to the direction cue. [Answer: ionization energy fits the falling direction but fails the scale (hundreds of kJ/mol, not values under 4); atomic radius fails the direction (it grows down a group while these values fall); also accepted: IE out on size only, radius out on direction (radius also fails on size — near a hundred picometers)] (c) The values fall going DOWN the group, so going UP the group they rise: each element sits above a lower-valued neighbor. The element one row above arsenic should therefore have a value HIGHER than arsenic's 2.18. It should still sit on the same scale, though — electronegativity's scale tops out near 4, so higher than 2.18 but below about 4. [Answer: higher than 2.18 (and still under the scale's ceiling near 4); also accepted: greater than arsenic's 2.18, since the trend rises going up the group | above 2.18 but on the same under-4 scale]