The decomposition of the nucleus is referred to as radioactive decay. During radioactive decay, an unstable nucleus spontaneously decomposes to form a different nucleus, giving off radiation in the form of atomic particles or high energy rays in an attempt to reach a more stable arrangement of its protons and neutrons .This decay occurs at a constant rate that is referred to as half-life. The stable nuclides exist in the zone of stability. A radionuclide that decays to another nuclide which may be either radioactive or stable is a parent nuclide; while a daughter nuclide is formed by the radioactive decay of a different nuclide. Radioactive nuclei can undergo decomposition in a variety of ways. The spontaneous decay process can produce particles as in the case of alpha, beta, or positron emission. The alternate form of emission is that of electromagnetic radiation such as x-rays or gamma-rays. An alpha particle is simply a helium nucleus which is ejected with high energy from an unstable nucleus. Beta particles are identical to electrons and thus have a negative charge. This type of decay process leaves the mass number of the nuclei unchanged. Positron is the opposite of beta decay. A ramification of alpha or beta particle production is that the newly formed nucleus is left in a state of excess energy. A way for the nucleus to release this excess energy is by emitting gamma rays. Since gamma rays have no mass, and are waves rather than particles, the elements atomic number does not change
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