The nuclear radiation emitted may be: • an alpha particle (α) – this consists of two neutrons and two protons; it is identical to the nucleus of a helium atom • a beta particle (β) – a high-speed electron ejected from the nucleus as a neutron turns into a proton • a gamma ray (γ) – electromagnetic radiation from the nucleus • a neutron (n).
Nuclear equations are used to represent radioactive decay.
In a nuclear equation an alpha particle may be represented by the symbol: 4 He 2 and a beta particle by the symbol: 0 e -1
The emission of the different types of ionising radiation may cause a change in the mass and/or the charge of the nucleus.
The emission of a gamma ray does not cause the mass or the charge of the nucleus to change.
Radioactive decay is random, so it is not possible to predict which individual nucleus will decay next. But with a large enough number of nuclei it is possible to predict how many will decay in a certain amount of time.
The half-life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in a sample to halve, or the average time it takes for the count rate from a sample containing a radioactive isotope to fall to half its initial level.
Count rate is the number of decays recorded each second by a detector (such as a Geiger– Müller tube)