Isotope

Isotopes are forms of an element whose nuclei have the same atomic number?-the number of protons in the nucleus--but different atomic masses because they contain different numbers of neutrons.

Occurrence in nature

Several isotopes of each element can be found in nature. The relative abundance of an isotope is strongly correlated with its tendency toward nuclear decay; short-lived nuclides quickly decay away, while their long-lived counterparts endure. However, this does not mean that short-lived species disappear entirely; many are continually produced through the decay of longer-lived nuclides. The tabulated atomic masses of elements are averages that account for the presence of multiple isotopes with different masses.

Related Topics:
Relative abundance - Nuclear decay - Atomic mass

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According to generally accepted cosmology, virtually all nuclides other than isotopes of hydrogen and helium were built in stars and supernovae. Their respective abundances here result from the quantities formed by these processes, their spread through the galaxy, and their rates of decay. After the initial coalescence of the solar system, isotopes were redistributed according to mass (see also Origin of the solar system). The isotopic composition of elements is different on different planets, making it possible to determine the origin of meteorites.

Related Topics:
Cosmology - Hydrogen - Helium - Star - Supernova - Galaxy - Solar system - Origin of the solar system - Meteorite

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