# Explain what happens during beta decay, including how the nucleus changes and what is emitted.

> WJEC GCSE Physics (Wales) — 2.9 Nuclear decay and nuclear energy · Explain · 4 marks

## Mark scheme (4 marks)

1. A neutron in the nucleus changes into a proton
2. The mass number / nucleon number stays the same (unchanged)
3. The atomic number / proton number increases by 1
4. A beta particle (fast-moving electron) is emitted from the nucleus

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Physics (Wales)](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-happens-during-beta-decay-73c82dbf) · Published by Druglandscape Ltd.