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GCSE Physics · key term
A model in which an atom has a tiny, positively charged central nucleus surrounded by electrons, with most of the atom being empty space.
Used by AQA and OCR
Specification 4.4.1.3 · Paper 1
Revise: The development of the model of the atomRutherford therefore developed the nuclear model in 1911: nearly all the mass and all the positive charge were concentrated in a tiny central nucleus, with electrons surrounding it. The plum pudding model was replaced because the nuclear model explained the new evidence whereas the old model did not.
Paper 1, Paper 2
The model in which an atom has a small, positively charged nucleus surrounded by electrons.
Revise: Atomic Structure and the Evolution of Atomic ModelsRutherford used this evidence to develop the nuclear model in 1911. It placed a tiny, massive, positively charged nucleus at the centre, with electrons in the much larger region around it. This explained both the mainly unobstructed paths and the occasional strong repulsions of alpha particles.
Keep the chronology clear: electron discovered in 1897 → plum pudding model proposed later → alpha scattering and nuclear model → Bohr’s fixed distances → proton → Chadwick’s neutron.
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