# Explain what is meant by the term 'isotopes' and describe how two isotopes of the same element are both similar and different in terms of their subatomic particles.

> Edexcel GCSE Chemistry (1CH0) — 1.3 Atomic structure · Explain · 4 marks

## Mark scheme (4 marks)

1. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
2. Two isotopes have the same number of protons (and the same number of electrons).
3. Two isotopes have different numbers of neutrons.
4. The difference in the number of neutrons means isotopes have different mass numbers (relative atomic masses).

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-what-is-meant-by-the-7470264f) · Published by Druglandscape Ltd.