Ionising Potential

Key Stage 4

Ionising potential is magnitude of the ionising effect of ionising radiation.

Ionising potential is related to the risk to living organisms of ionising radiation. The more highly ionising the more dangerous the ionising radiation if it is absorbed by living tissue.

With a charge of +2, α-particles are the most ionising of the three ionising radiations. It is capable of removing two electrons from a single atom or molecule or removing 1 electron from two atoms or molecules.


When an α-particle interacts with an atom the α-particle can remove one or two electrons to ionise the atom.

With a charge of -1, β-particles are the second most ionising of the three ionising radiations. It is capable of knocking out more than one electron from different atoms or molecules as it has a large amount of kinetic energy.


When a beta particle interacts with an atom the beta minus particle can pass on some of its kinetic energy to an electron in the outer shell causing the electron to escape ionising the atom. This may happen more than once if the beta particle collides with another atom with enough energy.

With no electrical charge, \(\gamma\)-rays are the least ionising of the three ionising radiations. It is capable of knocking out one electron from an atom or molecule by being absorbed by an electron in the [[Outer Shell|outer shell].


When a gamma-ray interacts with an atom the gammarray is absorbed by an electron in the outer shell causing the electron to escape ionising the atom.

With a charge of 0 and almost no effect on the electrons orbiting nuclei, neutrons are not directly ionising.

Neutron radiation is referred to as indirectly ionising because it does not affect the electrons orbiting an atom but it can cause the release of directly ionising radiation in two ways:

It can be absorbed by a nucleus making it unstable and causing it to release a gamma-ray.

It can decay into a proton and a beta particle releasing a gamma-ray.