GCSE Physics · AQA 8463 · Topic 4.4
Atomic structure
Key points
- An atom has a tiny, dense, positive nucleus (protons and neutrons) with electrons around it. Its radius is about m.
- Isotopes are atoms of the same element with different numbers of neutrons.
- The atomic model developed from the plum pudding model to the nuclear model (alpha scattering), then Bohr's energy levels and the discovery of the neutron.
- Unstable nuclei emit alpha particles, beta particles, gamma rays or neutrons. Activity is measured in becquerels (Bq).
- Half-life is the time for the number of unstable nuclei (or the activity) to halve. Decay is random.
- Contamination and irradiation are different hazards. Radiation is used in medicine for tracers and radiotherapy.
- Fission splits large nuclei; fusion joins small nuclei. Both release energy.
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Everything is made of atoms, and some atoms have unstable nuclei that give out radiation. This topic covers what atoms are made of, how our model of the atom developed, how radioactive decay works and how we use (and protect ourselves from)…
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