# Explain how the results of the gold foil experiment led Rutherford to propose the nuclear atomic model, and why these results could not be explained by Thomson's plum pudding model.

> OCR GCSE Chemistry A: Gateway Science (J248) — C1.2 Atomic structure · Explain · 4 marks

> In the early twentieth century, Geiger and Marsden fired alpha particles at a thin sheet of gold foil. Most alpha particles passed straight through, but a small number were deflected at large angles, and a very few bounced almost straight back.

## Mark scheme (4 marks)

1. Most alpha particles passing straight through shows that atoms are mostly empty space
2. The large-angle deflections / backscattering show that there is a small, dense, positively charged nucleus at the centre of the atom
3. In Thomson's plum pudding model the positive charge is spread evenly throughout the atom, so alpha particles would not be deflected at large angles / could not be deflected back
4. Only a small number of alpha particles are deflected because the nucleus is very small compared to the size of the atom / most alpha particles miss the nucleus

## Key terms

- [nuclear atomic model](https://www.gradenine.co.uk/glossary/nuclear-atomic-model)
- [plum pudding model](https://www.gradenine.co.uk/glossary/plum-pudding-model)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](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-results-of-the-a4460a85) · Published by Druglandscape Ltd.