# Explain what is meant by an isotope and describe how two isotopes of the same element are similar and how they differ.

> AQA A-Level Physics (7408) — 3.2.1 Particles · Explain · 5 marks

## Mark scheme (5 marks)

1. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons
2. Isotopes have different numbers of neutrons (in the nucleus)
3. Isotopes have the same number of electrons
4. Isotopes have the same chemical properties (because chemical properties depend on the number of electrons)
5. Isotopes have different mass numbers (because they have different numbers of neutrons, so the total number of particles in the nucleus differs)

## Key terms

- [isotope](https://www.gradenine.co.uk/glossary/isotope)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-what-is-meant-by-an-bcbc58fe) · Published by Druglandscape Ltd.