Different isotopes of one chemical element may have different radioactive properties. Those isotopes that are not radioactive are called stable. While stable isotopes of the same element maintain the same chemical characteristics and therefore react in the same way, the mass difference as a result of an extra few neutrons results in partial separation of the light from heavy isotopes during chemical reactions (isotopic fractionation). For example, the difference in mass between the two main isotopes of hydrogen H-1 (1 proton, no neutron) and H-2 (also known as deuterium; 1 proton, 1 neutron) is almost 100%. Therefore, a significant fractionation will occur.
Commonly analysed stable isotopes include oxygen, carbon, hydrogen and sulfur. These isotope systems have been under investigation for many years as they are relatively simple to measure. Recent advances in mass spectrometry (ie: muliple-collector inductively coupled plasma mass spectrometry) now enable the measurement of heavier stable isotopes, such as iron, copper, zinc, molybdenum, etc.
List of stable isotopes
see also: isotope table (complete) and isotope table (divided)
Among stableisotopes the most useful as biological tracers are the heavy isotopes of carbon and nitrogen.
Isotopes of the same element take part in the same chemical reactions, but because the atoms of different isotopes are of different sizes and different atomic weights they react at different rates.
Stableisotope analysis gives an independent measure of fractionation such that if, for instance, a sample is 1.5% heavier in 13C than "modern standard carbon" through the effects of fractionation, then it will be 3% heavier in 14C than it would have been had fractionation not taken place.
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.
The word isotope, meaning at the same place, comes from the fact that all isotopes of an element are located at the same place on the periodic table.
In scientific nomenclature, isotopes (nuclides) are specified by the name of the particular element by a hyphen and the number of nucleons (protons and neutrons) in the atomic nucleus (e.g., helium-3, carbon-12, carbon-14, iron-57, uranium-238).
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