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Day 8 · A negative ion has more electronsYear 11 Chemistry · T1 W1–2 · Day 8 lesson

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Year 11 / Chemistry / Term 1 / Weeks 01 02

Part of the full two-week lesson sequence. Check the pack guide and taught point before teaching.

Open for this lesson: Pack guide · Daily routes · Worked swaps · Fresh learner checks · Aids and text routes.

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Teacher copy: This page may include teaching prompts or answer keys. Answer keys in this public library can be viewed by anyone. Give learners a clean prompt, use checks as formative evidence, and change a case locally when prior access matters.

Learner prompts

Target: calculate electron gain for chlorine-35 1− and oxygen-16 2−, preserving A/Z. Prepare: Cards B/D and count mat; O Z 8, Cl Z 17.

  1. Launch · 2 min. Compare neutral chlorine-35 with a 1− card. Ask whether adding one electron changes its isotope name.
  2. Model · 4 min. Chlorine-35: p 17, n 18, neutral e 17; 1− e 18. Addition of an electron leaves A 35 and Z 17 fixed.
  3. Guided reading · 5 min. Oxygen-16 2−: p 8, n 8, e 10. Use charge as a check: eight positive protons against ten negative electrons gives net 2−.
  4. Practice route · 7 min. Choose Day 8 route; derive both full count triples, then describe electron gain with a qualifier that this is a paper species card.
  5. Audit · 4 min. Peer uses 2− as “lose two neutrons”; learner repairs with p/n/e and charge bookkeeping.
  6. Exit · 3 min. “What stayed the same from neutral oxygen-16 to its 2− ion?” Key: p 8, n 8, Z 8, A 16 and element/isotope name.

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