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Target: read/write the left A-over-Z symbol as full words and derive a neutral magnesium-26 and sodium-23 count. Prepare: Card C and count mat; give Mg Z 12 and Na Z 11.
Launch · 2 min. Show ^{26}_{12}Mg beside “magnesium-26, Z 12, neutral.” Ask which is isotope mass number versus element identifier.
Model · 4 min. Translate top-left A 26 and bottom-left Z 12; p 12, n 14, neutral e 12. The written convention is a model/notation, not a physical picture.
Guided reading · 5 min. Read ^{23}_{11}Na as sodium-23, Z 11, neutral for this task. Derive p 11, n 12, e 11. Model an accessible spoken sequence: “name, A, Z, charge.”
Practice route · 7 min. Choose Day 6 route; translate both symbols in both directions and check derived counts.
Audit · 4 min. Partner reads 26 as number of protons. Learner identifies position and verifies n = 26 − 12.
Exit · 3 min. “Where does A sit in nuclear notation?” Key: upper left of X; Z lower left.