# Explain how scientists' model of the atom changed as a result of the alpha particle scattering experiment. Your answer should include what the earlier model suggested and what the new evidence showed.

> Eduqas A-Level Physics — 1.7 Particles and nuclear structure · Explain · 5 marks

> In a famous experiment, a beam of alpha particles was fired at a thin gold foil. Most passed straight through, but a small number were deflected at large angles, and a very small number bounced almost straight back.

## Mark scheme (5 marks)

1. The earlier model (plum pudding model) suggested the atom was a ball of positive charge with electrons embedded throughout it
2. Most alpha particles passed straight through, showing the atom is mostly empty space
3. A small number of alpha particles were deflected at large angles / bounced back, showing a concentrated positive charge at the centre
4. The nucleus is very small compared to the overall size of the atom
5. The new model (nuclear model) placed the mass and positive charge concentrated in a small central nucleus with electrons orbiting around it

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level 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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-scientists-model-of-the-97bf8ca1) · Published by Druglandscape Ltd.