Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Chemistry
Lesson Topic: Deduce the formula of a simple compound from the relative numbers of atoms present in a model or a diagrammatic representation
Learning Objective/s:
  • Describe how to count atoms in a model or diagram.
  • Convert counted numbers to the simplest whole‑number ratio.
  • Write the empirical formula using the derived ratio.
  • Identify and correct common errors such as fractional subscripts.
  • Apply the procedure to solve practice problems independently.
Materials Needed:
  • Ball‑and‑stick model kits or printed diagrams
  • Whiteboard and markers
  • Projector or interactive whiteboard
  • Worksheets with practice questions
  • Calculator (optional)
 Introduction:
Begin with a quick visual of a ball‑and‑stick model and ask students what information they can extract. Recall that compounds are composed of atoms in whole‑number ratios, which they have used when balancing equations. Explain that today they will learn a systematic method to deduce the empirical formula from such models, and success will be measured by correctly writing formulas for three practice examples.
Lesson Structure:
  1. Do‑now (5'): Students examine a simple model and note the number of each atom (quick check).
  2. Mini‑lecture (10'): Review whole‑number ratios and the step‑by‑step procedure; demonstrate with H₂O example.
  3. Guided practice (15'): Whole‑class work through the MgCl₂ fractional‑ratio example, discussing division by the smallest number and multiplying to remove fractions.
  4. Independent practice (15'): Students complete three worksheet questions while the teacher circulates for support.
  5. Check for understanding (5'): Quick quiz – students write the empirical formula for a new model on sticky notes.
  6. Summary & reflection (5'): Teacher recaps key steps and highlights common pitfalls.
Conclusion:
Summarise the four‑step method: count, form a ratio, adjust to whole numbers, and write the formula. Ask students to write one formula on an exit ticket to demonstrate mastery. For homework, assign additional models to practice the procedure and prepare them for upcoming molecular‑formula calculations.