# Explain how the discovery of the neutron changed scientists' understanding of atomic structure, and state the relative charge of a neutron.

> Edexcel A-Level Chemistry (9CH0) — 1.1 Atomic structure · Explain · 5 marks

> Early models of the atom suggested that the nucleus contained only protons. In 1932, James Chadwick discovered a new subatomic particle.

## Mark scheme (5 marks)

1. States that the neutron has no charge / is neutral / relative charge of zero
2. States that neutrons are found in the nucleus
3. Explains that the existence of neutrons accounts for why atoms of the same element can have different masses
4. States that isotopes are atoms of the same element with different numbers of neutrons (or different mass numbers)
5. Explains that the mass number equals the total number of protons plus neutrons in the nucleus

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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-how-the-discovery-of-the-4ee8ba16) · Published by Druglandscape Ltd.