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Isotopes of sodium
There are twenty recognized isotopes of sodium, ranging from to and two isomers ( and ). is the only stable (and the only primordial) isotope. As such, it is considered a monoisotopic element and it has a standard atomic mass: . Sodium has two radioactive cosmogenic isotopes (, half-life = 2.605 years; and , half-life ≈ 15 hours). With the exception of those two, all other isotopes have half-lives under a minute, most under a second. The least stable is , with a half-life of seconds.
Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable in human blood plasma to . By measuring the concentration of this isotope, the neutron radiation dosage to the victim can be computed.
is a positron-emitting isotope with a remarkably long half-life. It is used to create test-objects and point-sources for positron emission tomography.
== Table ==
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抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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