Lesson Plan

• Define an isotope and distinguish it from the element itself.
• Explain why a single element can possess multiple isotopes.
• Interpret isotope notation (Z, N, A) and calculate mass numbers.
• Compare physical properties of isotopes using carbon as an example.
• Compose a concise exam‑style response describing isotopes and multiple isotopes per element.

• Projector or interactive whiteboard
• PowerPoint slides with isotope diagrams
• Printed worksheet containing the carbon isotope table
• Nucleus model kit (or 3‑D printed models)
• Whiteboard and markers
• Exit‑ticket cards for the conclusion

Start with a quick poll: “Who has heard of carbon‑14 dating?” Connect this to prior knowledge of atomic structure, then state the success criteria – students will be able to define isotopes, explain why an element can have several, and use correct notation.

1. Do‑now (5') – Students list any isotopes they know and share why they think they differ.
2. Mini‑lecture (10') – Definition of isotope, notation (Z, N, A) and key points about chemical vs. physical properties.
3. Guided analysis (10') – Examine the carbon isotope table; calculate mass numbers and discuss natural abundance.
4. Concept check (5') – Think‑pair‑share: “Why can an element have more than one isotope?”
5. Interactive demo (10') – Use nucleus models to add/remove neutrons and observe unchanged proton count.
6. Exam practice (10') – Students write a short answer using the key statement for exam responses; peer review.

Recap the definition of isotopes and the reason an element may have several, highlighting the carbon example. Students complete an exit ticket summarising the key statement, and for homework they research another element’s isotopes and prepare a brief table.