Ionising radiation
The radiation emitted from unstable nuclei is called ionising radiation because as it passes through matter it can dislodge outer electrons from atoms causing them to become ions.
Types of radioactive decay
An unstable nucleus can decay by emitting an alpha particle, a beta particle, or a gamma ray.
Alpha particle
An alpha particle is a âpackageâ of two protons and two neutrons emitted from an unstable nucleus to become more stable.
Alpha radiation is a stream of alpha particles emitted from unstable nuclei.
An alpha particle is made up of two protons and two neutrons which is the same as a helium nucleus.
For this reason, an alpha particle is sometimes called a helium nucleus.
It is written as \(_{2}^{4}\textrm{He}\) or \(_{2}^{4}\alpha\).
An example of alpha decay
Alpha decay of Uranium-238:
\(_{92}^{238}\textrm{U}\rightarrow_{90}^{234}\textrm{Th}+_{2}^{4}\textrm{He}\)
Alpha particles are relatively:
- Large.
- Heavy.
- Slow.
Beta particle
A beta particle is a fast-moving electron emitted from an unstable nucleus to become more stable.
It is written as \(_{-1}^{~0}\textrm{e}\) or \(_{-1}^{~0}\beta\).
Beta radiation is a stream of beta particles emitted from unstable nuclei.
Electrons are not normally found in the nucleus but, in an unstable nucleus, a neutron can split into a positive proton and a negative electron.
The proton remains inside the nucleus, but the electron is ejected at high speed.
This is called beta decay.
An example of beta decay carbon-14
Beta decay of carbon-14:
\(_{6}^{14}\textrm{C}\rightarrow_{7}^{14}\textrm{N}+_{-1}^{0}\textrm{e}\)
Beta particles are relatively:
- Small.
- Light.
- Fast.