Nuclear Physics

Nuclear physics deals with the structure of atomic nuclei and the processes by which they change. This topic covers the nuclear model, radioactivity, nuclear decay, the exponential decay law, binding energy, and the processes of fission and fusion. It is tested in AQA Paper 2 (Section 8) and OCR Paper 2 (Module 6). This material also connects with the particle physics covered earlier in the course.

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The Nucleus and the Nuclear Model

The nucleus contains protons and neutrons (collectively called nucleons). The nucleus is described by:

• Atomic number (Z) — the number of protons (defines the element)
• Mass number (A) — the total number of nucleons (protons + neutrons)
• Neutron number (N) — the number of neutrons, N = A − Z
• Isotopes — atoms with the same number of protons but different numbers of neutrons

Rutherford Scattering and the Nuclear Model

Ernest Rutherford's alpha-particle scattering experiment (1909, conducted by Geiger and Marsden) was pivotal in establishing the nuclear model of the atom.

The experiment: A beam of alpha particles was fired at a thin gold foil. Detectors (zinc sulphide screens) around the foil recorded where the alpha particles arrived.