Fluorine (9F) has 18 known isotopes ranging from to (with the exception of ) and two isomers ( and ). 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 ; it has a half-life of . 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 , whose half-life is , corresponding to a resonance width of . List of isotopes |- | | style="text-align:right" | 9 | style="text-align:right" | 4 | # | | p ? | ? | 1/2+# | | |- | | style="text-align:right" | 9 | style="text-align:right" | 5 | | [] | p ? | ? | 2− | | |- | | style="text-align:right" | 9 | style="text-align:right" | 6 | | [] | p | | 1/2+ | | |- | | style="text-align:right" | 9 | style="text-align:right" | 7 | | [] | p | | 0− | | |- | | style="text-align:right" | 9 | style="text-align:right" | 8 | | | β+ | | 5/2+ | | |- | | style="text-align:right" | 9 | style="text-align:right" | 9 | | | β+ | | 1+ | Trace | |- | style="text-indent:1em" | | colspan="3" style="text-indent:2em" | | | IT | | 5+ | | |- | | style="text-align:right" | 9 | style="text-align:right" | 10 | | colspan=3 align=center|Stable | 1/2+ | colspan=2 style="text-align:center"|1 |- | | style="text-align:right" | 9 | style="text-align:right" | 11 | | | β− | | 2+ | | |- | | style="text-align:right" | 9 | style="text-align:right" | 12 | | | β− | | 5/2+ | | |- | rowspan=2| | rowspan=2 style="text-align:right" | 9 | rowspan=2 style="text-align:right" | 13 | rowspan=2| | rowspan=2| | β− (> ) | | rowspan=2|(4+) | rowspan=2| | rowspan=2| |- | β−n (< ) | |- | rowspan=2| | rowspan=2 style="text-align:right" | 9 | rowspan=2 style="text-align:right" | 14 | rowspan=2| | rowspan=2| | β− (> ) | | rowspan=2|5/2+ | rowspan=2| | rowspan=2| |- | β−n (< ) | |- | rowspan=2| | rowspan=2 style="text-align:right" | 9 | rowspan=2 style="text-align:right" | 15 | rowspan=2| | rowspan=2| | β− (> ) | | rowspan=2|3+ | rowspan=2| | rowspan=2| |- | β−n (< ) | |- | rowspan=3| | rowspan=3 style="text-align:right" | 9 | rowspan=3 style="text-align:right"