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.

Applications of isotopes

Several applications exist that capitalize on properties of the various isotopes of a given element.

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Use of chemical properties

• One of the most common applications is isotopic labeling, the use of unusual isotopes as tracers or markers in chemical reactions. Normally, atoms of a given element are indistinguishable from each other. However, by using isotopes of different masses, they can be distinguished by mass spectrometry or infrared spectroscopy (see "Properties"). If radioactive isotopes are used, they can be detected by the radiation they emit (this is radioisotopic labelling).
• A technique similar to radioisotopic labelling is radiometric dating (most famously radiocarbon dating). It can be used to study chemical processes that the experimenter does not witness, by using naturally-occurring isotopic tracers.
• Isotopic substitution can be used to determine the mechanism of a reaction via the kinetic isotope effect.

Use of nuclear properties

• Several forms of spectroscopy rely on the unique nuclear properties of specific isotopes. For example, nuclear magnetic resonance (NMR) spectroscopy can be used only for isotopes with a nonzero nuclear spin. The most common isotopes used with NMR spectroscopy are ¹H, ²D, ¹³C, and ³¹P.
• Mössbauer spectroscopy also relies on the nuclear transitions of specific isotopes, such as ⁵⁷Fe.
• Radionuclides also have important uses. Nuclear power and nuclear weapons development require relatively large quantities of specific isotopes. The process of isotope separation represents a significant technological challenge.