Radioactivity is the emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei. Various isotopes undergo spontaneous disintegration emitting different types or particles and the reaction in fission and fusion reactors also emit different particles.
The list below gives some possible emissions:
- Alpha decay occurs when the nucleus ejects an alpha particle (helium nucleus).
- Beta decay occurs in two ways; beta-minus decay, when the nucleus emits an electron and an antineutrino in a process that changes a neutron to a proton and beta-plus decay, when the nucleus emits a positron and a neutrino in a process that changes a proton to a neutron, also known as positron emission.
- In gamma decay a radioactive nucleus first decays by the emission of an alpha or beta particle. The daughter nucleus that results is usually left in an excited state and it can decay to a lower energy state by emitting a gamma ray photon.
- In neutron emission, extremely neutron-rich nuclei, formed due to other types of decay or after many successive neutron captures, occasionally lose energy by way of neutron emission, resulting in a change from one isotope to another of the same element.
- In electron capture, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. A neutrino and a gamma ray are subsequently emitted.
- In cluster decay and nuclear fission, a nucleus heavier then an alpha particle is emitted.
Further details on radioactivity are give on the pages: