Isotopes of fluorine

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 mononuclidic element.

The longest-lived radioisotope is ¹⁸
F
; it has a half-life of 109.734(8) min. All other fluorine isotopes have half-lives of less than a minute, and most of those less than a second. The least stable known isotope is ¹⁴
F
, whose half-life is 500(60) yoctoseconds,^[4] corresponding to a resonance width of 910(100) keV.