# Describe what is meant by alpha decay and explain why the nucleus of an atom undergoes radioactive decay.

> WJEC GCSE Physics (Wales) — 2.4 The atom, the nucleus and radioactivity · Describe and Explain · 4 marks

> Unstable nuclei can emit different types of radiation. One type of decay involves the emission of an alpha particle.

## Mark scheme (4 marks)

1. An alpha particle consists of 2 protons and 2 neutrons (a helium nucleus)
2. The proton number (atomic number) decreases by 2 and the mass number decreases by 4
3. Radioactive decay occurs because the nucleus is unstable
4. Radioactive decay is a random process / cannot predict when a particular nucleus will decay

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/describe-what-is-meant-by-alpha-f5dac90f) · Published by Druglandscape Ltd.