Types of Ionising Radiation

Ever wondered why some radiation is more dangerous than others? It all comes down to three main types that have completely different properties and abilities to penetrate materials.

Alpha radiation consists of 2 protons and 2 neutrons (basically a helium nucleus) with a +2 charge and mass of 4. It's the most ionising but least penetrating - it can only travel a few centimetres in air and is stopped by paper or skin.

Beta radiation is high-energy electrons with a -1 charge and virtually no mass (1/2000th of a proton). It has medium ionising power and can penetrate about 200 metres in air, but aluminium foil will stop it.

Gamma radiation is high-energy electromagnetic waves with no charge or mass. It's the least ionising but most penetrating - it can travel very long distances and requires thick lead or concrete to stop it.

Quick Tip: Remember the penetrating power order: Alpha < Beta < Gamma, but ionising power is the complete opposite!

The general equations show how nuclei change: alpha decay reduces the mass number by 4 and atomic number by 2, whilst beta decay increases the atomic number by 1 but keeps the same mass number.