Radioactive Isotopes

Synonyms

Radioisotopes; Radionuclides; Unstable isotopes

Definition

Radioactive isotopes are the atoms with unstable nucleus which decay with time by emitting different types of particles or radiations such as neutrons, electrons (beta particles), etc. or gamma radiations (see Radioactivity ).

Origin

Naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides. Primordial radionuclides originate mainly from the interiors of stars and, like uranium and thorium, are still present because their half-lives are so long that they have not yet completely decayed. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Artificially produced radionuclides can be produced by nuclear...