EnvThes
stable isotope
deprecated concept
US LTER controlled vocabulary
Some isotopes are radioactive, and are therefore described as radioisotopes or radionuclides, while others have never been observed to undergo radioactive decay and are described as stable isotopes or stable nuclides. For example, 14C is a radioactive form of carbon while 12C and 13C are stable isotopes. Elements are composed of one or more naturally occurring isotopes. All the known stable isotopes occur naturally on Earth. Isotope analysis is the determination of isotopic signature, the relative abundances of isotopes of a given element in a particular sample. For biogenic substances in particular, significant variations of isotopes of C, N and O can occur.