Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Chemistry
Lesson Topic: Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation or from the charges on the ions
Learning Objective/s:
  • Identify the charges of common cations and anions.
  • Apply the charge‑balance method to write correct formulas for ionic compounds.
  • Use subscripts and parentheses appropriately for polyatomic ions.
  • Interpret model diagrams to determine ion ratios.
  • Verify that total positive and negative charges are equal in the final formula.
Materials Needed:
  • Projector and screen
  • Whiteboard and markers
  • Printed worksheet with ion charge table
  • Ball‑and‑stick model kits (ions)
  • Periodic‑table handouts
  • Calculator (optional)
 Introduction:
Begin with a quick visual of a ball‑and‑stick model showing Na⁺ ions surrounding a PO₄³⁻ ion to spark curiosity. Review that ionic compounds must be electrically neutral and that students already know cation and anion charges. Explain that today they will learn a step‑by‑step method to deduce formulas and will demonstrate mastery through guided practice.
Lesson Structure:
  1. Do‑Now (5'): Students write formulas for three given ion pairs on a sticky note.
  2. Mini‑lecture (10'): Introduce the charge‑balance method, show the step‑by‑step procedure, and work through the MgCl₂ example.
  3. Guided Practice (15'): Whole‑class walk‑through of the Na₃PO₄ model example, discussing each step.
  4. Independent Practice (15'): Students complete a worksheet with five practice questions while the teacher circulates.
  5. Exit Ticket (5'): Write the formula for Fe³⁺ combined with S²⁻; submit before leaving.
Conclusion:
Recap the five‑step charge‑balance process and emphasise checking that the total charge is zero. Collect the exit tickets as a quick retrieval check. For homework, assign additional worksheet problems that require students to balance charges for both simple and polyatomic ions.