# A radioactive nucleus emits a beta particle during nuclear decay. Explain what a beta particle is, describe what happens to the nucleus when it is emitted, and explain why the nucleus changes into a different element.

> WJEC A-Level Physics (Wales) — 3.5 Nuclear decay · Explain · 5 marks

## Mark scheme (5 marks)

1. A beta particle is a fast-moving electron
2. The beta particle is emitted from the nucleus when a neutron changes into a proton
3. The proton number (atomic number) increases by one
4. The mass number (nucleon number) stays the same / is unchanged
5. Because the proton number determines the element, a higher proton number means it is a different element

## Key terms

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

## Related

- [Revision notes for WJEC A-Level 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/a-radioactive-nucleus-emits-a-beta-3e6052ee) · Published by Druglandscape Ltd.