alpha beta gamma radiation table.doc

All substance are made of atoms. These have electrons (e) around the outside, and a nucleus in the middle. The nucleus consists of protons (p) and neutrons (n),  and is extremely small. (Atoms are almost entirely made of empty space!) In some types of atom, the nucleus is unstable, and will decay into a more stable atom. This radioactive decay is completely spontaneous.

Radioactivity refers to the particles which are emitted from nuclei as a result of nuclear instability.

• helium nuclei – 42 He
• big and heavy (slow moving)
• don’t penetrate into materials
• very ionising
• blocked by paper

• high-energy electrons – -10 e
• quite small, move quite fast
• penetrate materials moderately
• ionise moderately
• (for every beta particle emitted, a neutron turns into a proton in the nucleus)
• blocked by thin Aluminium

• electromagnetic waves with shorter wavelength (higher frequency) than x-rays
• opposite to alpha
• penetrate materials well
• weakly ionising
• when hit something do damage
• blocked by thick lead

Gamma rays are waves, not particles. This means that they have no mass and no charge.