What is radioactivity? Compare the properties of alpha, beta and gamma radiations.

1. 1 · Define radioactivity. Spontaneous break-up of unstable nuclei with emission of α, β or γ radiation; heat and pressure do not affect it.
2. 2 · Say what each is. α: helium nucleus (+2e); β: fast electron (−e); γ: electromagnetic wave with no charge.
3. 3 · Compare ionising power. α > β > γ.
4. 4 · Compare penetrating power. γ > β > α: α stopped by paper, β by a few mm of aluminium, γ needs several cm of lead.
5. 5 · Draw the paths in a magnetic field. [Diagram: source in a lead block; α bends slightly one way, β sharply the other way, γ goes straight]
6. 6 · Close in one line. So, α and β change the element, while γ only carries away energy.

Scoring tip: A neat three-column table for α, β and γ is the quickest way to full marks here.