| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: State that isotopes of the same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration |
Learning Objective/s:
- Describe the definition of an isotope and identify protons, neutrons, and electrons in isotopic notation.
- Explain why isotopes of the same element exhibit identical chemical behaviour.
- Interpret isotopic data (mass number, natural abundance) to compare nuclear differences.
- Apply the concept of electronic configuration to predict chemical reactions of isotopes.
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Materials Needed:
- Projector and screen
- PowerPoint/Google Slides presentation
- Handout with isotope tables and diagrams
- Periodic table poster
- Worksheet for guided practice
- Whiteboard and markers
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Introduction:
Begin with a quick “mystery element” challenge to spark curiosity about atoms that look the same but weigh differently. Review the concepts of protons, neutrons, and electrons, reminding students that chemical behaviour depends on electron arrangement. State that today’s success criteria are to explain why isotopes share chemical properties and to use isotopic notation correctly.
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Lesson Structure:
- Do‑now (5'): Students complete a short quiz on atomic structure on the board.
- Mini‑lecture (10'): Present definition of isotopes, nuclear composition, and electronic configuration using slides.
- Guided practice (12'): Work through the isotope table, identifying protons, neutrons, and mass numbers; discuss why electrons stay constant.
- Demonstration (8'): Show a diagram of two isotopes with identical electron shells but different nuclei; ask “What stays the same? What changes?”
- Collaborative activity (10'): In pairs, students analyse a worksheet comparing carbon and chlorine isotopes, then justify chemical similarity.
- Check for understanding (5'): Quick exit poll – one‑sentence answer to “Why do isotopes behave the same chemically?”
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Conclusion:
Recap the key point that identical electron counts give isotopes the same chemical properties, while neutron differences affect only mass and stability. Collect exit tickets to gauge understanding and assign a short homework: write a paragraph describing an isotope of their choice and explain its chemical behaviour.
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