Isotopes of fluorine
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| Standard atomic weight Ar°(F) | ||||||||||||||||||||||||||
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Fluorine (9F) has 19 known isotopes ranging from 13
F to 31
F and two isomers (18m
F and 26m
F). Only fluorine-19 is stable and naturally occurring in more than trace quantities; therefore, fluorine is a monoisotopic and a mononuclidic element.
The longest-lived radioisotope is 18
F with a half-life of 109.734 minutes, followed by 17
F with 64.37 seconds. These unstable isotopes participate in the CNO cycle within stars. All other fluorine isotopes have half-lives of less than 12 seconds, and most of those less than 1/2 second.