Nuclear Physics

What these notes cover

These notes cover nuclear physics for Cambridge O Level Physics (5054) and Cambridge IGCSE Physics (0625): the structure of the atom and its nucleus, isotopes and nuclide notation, and radioactivity, including alpha, beta and gamma emissions, background radiation, half-life and the safe handling of radioactive sources.

Key formulas and definitions

• Nucleon number (A) = protons + neutrons; proton number (Z) = protons. Number of neutrons = A − Z.
• Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
• Alpha decay: A decreases by 4 and Z decreases by 2.
• Beta (β⁻) decay: a neutron changes into a proton and an electron; Z increases by 1 and A is unchanged.
• Gamma emission: no change in A or Z.
• Half-life: the time taken for half the nuclei in a sample to decay; after n half-lives the fraction remaining is (½)ⁿ.
• Ionising ability: alpha > beta > gamma; penetrating ability: gamma > beta > alpha.