Definition of Radioactive

"Radioactive" and "Radioactivity" redirect here. For other uses see Radioactive (disambiguation).

For decay rate in a more general context see Particle decay.

Radioactive decay is the process in which an unstable  atomic nucleus  loses energy by emitting radiation in the form of particles or electromagnetic waves. This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide. For example: a carbon-14 atom (the "parent") emits radiation and transforms to a nitrogen-14 atom (the "daughter.") This is a random process on the atomic level, in that it is impossible to predict when a particular atom will decay, but given a large number of similar atoms, the decay rate, on average, is predictable.