# Explain what happens to the nucleus of an atom during alpha decay, including what an alpha particle is and how the nucleus changes.

> WJEC A-Level Physics (Wales) — 1.7 Particles and nuclear structure · Explain · 5 marks

> Unstable nuclei can emit radiation in a process called radioactive decay. One type of decay involves the emission of an alpha particle.

## Mark scheme (5 marks)

1. An alpha particle consists of 2 protons and 2 neutrons (equivalent to a helium nucleus)
2. The nucleus loses 2 protons, so the atomic/proton number decreases by 2
3. The nucleus loses 2 neutrons, so the mass/nucleon number decreases by 4
4. The nucleus of a different element is formed / the element changes
5. Alpha decay occurs because the nucleus is unstable and emits the alpha particle to become more stable

## Key terms

- [alpha particle](https://www.gradenine.co.uk/glossary/alpha-particle)
- [nucleus](https://www.gradenine.co.uk/glossary/nucleus)

## 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/explain-what-happens-to-the-nucleus-3a600d10) · Published by Druglandscape Ltd.