Radioactive decay

• 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)