# Public teacher-facing worked key and next moves

This answer page is **public by URL**. Days 5/10 are useful first-encounter formative prompts only when learners have not previewed it; use locally authored parallel files if previous access matters. Record original work and the support used. A correct dictated/AAC calculation can show the Chemistry target even when reading was supported; it does **not** establish independent reading. A supplied chemistry step or answer makes the response supported. None of these responses is a QCAA Unit 1 grade or school assessment instrument.

| Day | Worked target answer | If the learner gets stuck, next teaching move |
| --- | --- | --- |
| 1 | Nucleus contains positive protons and neutral neutrons; negative electrons are modelled outside at distinct energy levels. The rings are **not measured circular paths**. | Point to Card A's “model” label; ask learner to separate a drawn convention from an observation. |
| 2 | C Z6→6 protons; O Z8→8; Mg Z12→12. Story labels such as “fibre” do not identify an element without given chemical evidence. Z alone does not give neutron count. | Cover symbols and match given Z to the symbol table, then uncover and explain. |
| 3 | Neutral C-12: p6 n6; O-16: p8 n8; Mg-24: p12 n12. Check 6+6=12, 8+8=16, 12+12=24. A is an integer nucleon count for one isotope; periodic atomic weight can be a decimal average. | Use the count mat's `A = p+n` line, then physically move Z p-tokens away from A total tokens. |
| 4 | C-12/C-13: same Z6, n6/n7. Cl-35/Cl-37: same Z17, n18/n20. Both pairs are different isotopes of their respective element. The cards give no natural abundance. | Ask which number must stay equal for “same element”; calculate n with `A−Z` twice. |
| 5 | See full File R/S work below. | Revisit only the failed count or inference, then give a different local pair. |
| 6 | `^{26}_{12}Mg`: magnesium-26, A26 Z12 neutral by task convention; p12 n14 e12. `^{23}_{11}Na`: sodium-23, A23 Z11 neutral; p11 n12 e11. A is upper left, Z lower left. | Read “name, A, Z, charge” aloud, then calculate each count without using the decimal periodic weight. |
| 7 | Neutral Na-23 p11 n12 e11 → Na-23 1+ p11 n12 e10. Neutral Mg-24 p12 n12 e12 → Mg-24 2+ p12 n12 e10. Positive charge follows electron loss from same nuclide; nuclei stay fixed. | Keep proton/neutron tokens glued to the paper card and remove only electron counters. |
| 8 | Neutral Cl-35 p17 n18 e17 → Cl-35 1− p17 n18 e18. Neutral O-16 p8 n8 e8 → O-16 2− p8 n8 e10. A/Z remain fixed. Charge checks 17−18=−1 and 8−10=−2. | Add electron counters without moving p/n; have learner verify with p−e. |
| 9 | Plus charge in the same nuclide model means **fewer electrons**, not more protons; C-12/C-13 share Z6 so are same element/different isotopes; 23 in Na-23 is A, while Na has Z11; fictional catalogue label does not prove purity/composition. | Ask learner to point to the exact given symbol/status, then name the rule and unsupported leap. |
| 10 | See full File T/U work below. | Target the first count rule that broke, then use a different locally unseen charged card. |

## Day 5 Check A · worked File R/S key

| File | Z | A | protons p | neutrons n = A−Z | neutral electrons e | reverse check |
| --- | ---: | ---: | ---: | ---: | ---: | --- |
| R · boron-10 | 5 | 10 | 5 | 10−5=5 | 5 | 5+5=10 |
| S · boron-11 | 5 | 11 | 5 | 11−5=6 | 5 | 5+6=11 |

They are **two isotopes of boron**: both have Z5/five protons, while neutron count and A differ. They are not different elements and not the same isotope. A full-word reading of R is “boron-10, mass number 10, atomic number 5, neutral atom”; S substitutes 11. Neither fictional file reports actual ceramic content, relative abundance, dose, suitability or safety. **Next move:** if p/e are confused, compare the explicit “neutral” word with `e=Z`; if n was added, reverse-check p+n; if isotope classification fails, line up the two Z cards before looking at A. Preserve first response and give an unseen local pair for recheck.

## Day 10 Check B · worked File T/U key

| File | Z | A | protons p | neutrons n = A−Z | ion electrons e | charge check | same-isotope neutral e |
| --- | ---: | ---: | ---: | ---: | ---: | --- | ---: |
| T · calcium-40 2+ | 20 | 40 | 20 | 40−20=20 | 20−2=18 | 20−18=+2 | 20 |
| U · fluorine-19 1− | 9 | 19 | 9 | 19−9=10 | 9+1=10 | 9−10=−1 | 9 |

In each neutral-to-ion comparison, **electron number changes** while p, n, Z, A, element and isotope remain fixed. T and U are **not isotopes of each other**: Z20 versus Z9 means different elements. The cards cannot prove that a real transit sign/conserved item contains those ions, that an isolated ion is stable in a particular environment, how a reaction occurred or whether a material is safe. **Next move:** if a student changes proton count to account for charge, keep the nucleus strip in place and change only electron counters; if they call T/U isotopes, compare Z before A; if they infer product composition, return to the word “fictional.” Recheck with a newly written local card.

**Arithmetic audit:** every p, n and e entry above follows `p=Z`, `n=A−Z`, `e=Z` if neutral, and `p−e=q` for monoatomic charge q in elementary-charge units. [The local verifier](../verify_pack.py) independently recomputes the check triples and selected practice triples from structured constants; the above tables must agree. Chemical status is *given* by each paper card, not produced in a lab.

SubjectNest original worked key © NeuroForgeIO Pty Ltd 2026, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).