# Explain why some atoms are radioactive and describe what happens to the nucleus of a radioactive atom when it emits an alpha particle.

> Eduqas GCSE Physics — 2.4 The atom, the nucleus and radioactivity · Explain · 4 marks

> All atoms contain a nucleus made up of protons and neutrons. Some nuclei are unstable and emit radiation spontaneously.

## Mark scheme (4 marks)

1. A radioactive nucleus is unstable
2. The nucleus emits radiation spontaneously / randomly to become more stable
3. An alpha particle consists of 2 protons and 2 neutrons
4. The nucleus loses 2 protons and 2 neutrons so its proton number decreases by 2 and its nucleon/mass number decreases by 4

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Physics](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-some-atoms-are-radioactive-fb0fa4c9) · Published by Druglandscape Ltd.