Radioactivity is a spontaneous process characteristic of atoms with unstable nuclei in which the nucleus releases energy either as a particle with kinetic energy or as electromagnetic energy. Upon release of this energy the nucleus
may be stable or it may still be unstable and will acquire stability through an additional transformation(s). The original species prior to radioactive disintegration is often termed the ‘parent’ with the species after the transformation called the ‘daughter’ or ‘progeny’. A given transformation (one parent/daughter transition) is termed a ‘disintegration’ or a ‘decay’. The rate of radioactive disintegration is often used to indicate the ‘radioactivity’ of a sample and is termed the activity.