Radioactive decay
Radioactive decay, also known as
nuclear decay or
radioactivity, is the process by which a nucleus of an unstable atom loses energy by emitting ionizing radiation. A material that spontaneously emits this kind of radiation—which includes the emission of alpha particles, beta particles, and gamma rays—is considered
radioactive. Radioactive decay is a stochastic process at the level of single atoms, in that, according to quantum theory, it is impossible to predict when a particular atom will decay. However, the chance that a given atom will decay is constant over time. For a large number of atoms, the decay rate for the collection is computable from the measured decay constants of the nuclides. There are many different types of radioactive decay. A decay, or loss of energy, results when an atom with one type of nucleus, called the
parent radionuclide, transforms into an atom with a nucleus in a different state, or to a different nucleus containing different numbers of protons and neutrons. Either of these products is named the
daughter nuclide.