# Isotopes of fluorine

Fluorine ($_9$F) 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, corresponding to a resonance width of 910(100) keV.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Isotopic abundance |
| Isotopic abundance |||
| $^{13}$ F | 9 | 4 | 13.045120(540)# | | p ? | $^{12}$ O ? | 1/2+# | |
| $^{14}$ F | 9 | 5 | 14.034320(40) | 500(60) ys [910(100) keV] | p ? | $^{13}$ O ? | 2− | |
| $^{15}$ F | 9 | 6 | 15.017785(15) | 1.1(3) zs [376 keV] | p | $^{14}$ O | 1/2+ | |
| $^{16}$ F | 9 | 7 | 16.011460(6) | 21(5) zs [21.3(5.1) keV] | p | $^{15}$ O | 0− | |
| $^{17}$ F | 9 | 8 | 17.00209524(27) | 64.370(27) s | β$^+$ | $^{17}$ O | 5/2+ | |
| $^{18}$ F | 9 | 9 | 18.0009373(5) | 109.734(8) min | β$^+$ | $^{18}$ O | 1+ | Trace |
| $^{18m}$ F | 1121.36(15) keV | 1121.36(15) keV | 1121.36(15) keV | 162(7) ns | IT | $^{18}$ F | 5+ | |
| $^{19}$ F | 9 | 10 | 18.998403162067(883) | Stable | Stable | Stable | 1/2+ | 1 |
| $^{20}$ F | 9 | 11 | 19.99998125(3) | 11.0062(80) s | β$^−$ | $^{20}$ Ne | 2+ | |
| $^{21}$ F | 9 | 12 | 20.9999489(19) | 4.158(20) s | β$^−$ | $^{21}$ Ne | 5/2+ | |
| $^{22}$ F | 9 | 13 | 22.002999(13) | 4.23(4) s | β$^−$ (> 89%) | $^{22}$ Ne | (4+) | |
| $^{22}$ F | 9 | 13 | 22.002999(13) | 4.23(4) s | β$^−$n (< 11%) | $^{21}$ Ne | (4+) | |
| $^{23}$ F | 9 | 14 | 23.003530(40) | 2.23(14) s | β$^−$ (> 86%) | $^{23}$ Ne | 5/2+ | |
| $^{23}$ F | 9 | 14 | 23.003530(40) | 2.23(14) s | β$^−$n (< 14%) | $^{22}$ Ne | 5/2+ | |
| $^{24}$ F | 9 | 15 | 24.008100(100) | 384(16) ms | β$^−$ (> 94.1%) | $^{24}$ Ne | 3+ | |
| $^{24}$ F | 9 | 15 | 24.008100(100) | 384(16) ms | β$^−$n (< 5.9%) | $^{23}$ Ne | 3+ | |
| $^{25}$ F | 9 | 16 | 25.012170(100) | 80(9) ms | β$^−$ (76.9(4.5)%) | $^{25}$ Ne | (5/2+) | |
| $^{25}$ F | 9 | 16 | 25.012170(100) | 80(9) ms | β$^−$n (23.1(4.5)%) | $^{24}$ Ne | (5/2+) | |
| $^{25}$ F | 9 | 16 | 25.012170(100) | 80(9) ms | β$^−$2n ? | $^{23}$ Ne ? | (5/2+) | |
| $^{26}$ F | 9 | 17 | 26.020050(110) | 8.2(9) ms | β$^−$ (86.5(4.0)%) | $^{26}$ Ne | 1+ | |
| $^{26}$ F | 9 | 17 | 26.020050(110) | 8.2(9) ms | β$^−$n (13.5(4.0)%) | $^{25}$ Ne | 1+ | |
| $^{26}$ F | 9 | 17 | 26.020050(110) | 8.2(9) ms | β$^−$2n ? | $^{24}$ Ne ? | 1+ | |
| $^{26m}$ F | 643.4(1) keV | 643.4(1) keV | 643.4(1) keV | 2.2(1) ms | IT (82(11)%) | $^{26}$ F | (4+) | |
| $^{26m}$ F | 643.4(1) keV | 643.4(1) keV | 643.4(1) keV | 2.2(1) ms | β$^−$n (12(8)%) | $^{25}$ Ne | (4+) | |
| $^{26m}$ F | 643.4(1) keV | 643.4(1) keV | 643.4(1) keV | 2.2(1) ms | β$^−$ ? | $^{26}$ Ne ? | (4+) | |
| $^{27}$ F | 9 | 18 | 27.026980(130) | 5.0(2) ms | β$^−$n (77(21)%) | $^{26}$ Ne | 5/2+# | |
| $^{27}$ F | 9 | 18 | 27.026980(130) | 5.0(2) ms | β$^−$ (23(21)%) | $^{27}$ Ne | 5/2+# | |
| $^{27}$ F | 9 | 18 | 27.026980(130) | 5.0(2) ms | β$^−$2n ? | $^{25}$ Ne ? | 5/2+# | |
| $^{28}$ F | 9 | 19 | 28.035860(130) | 46 zs | n | $^{27}$ F | (4−) | |
| $^{29}$ F | 9 | 20 | 29.043100(560) | 2.5(3) ms | β$^−$n (60(40)%) | $^{28}$ Ne | (5/2+) | |
| $^{29}$ F | 9 | 20 | 29.043100(560) | 2.5(3) ms | β$^−$ (40(40)%) | $^{29}$ Ne | (5/2+) | |
| $^{29}$ F | 9 | 20 | 29.043100(560) | 2.5(3) ms | β$^−$2n ? | $^{27}$ Ne ? | (5/2+) | |
| $^{30}$ F | 9 | 21 | 30.05256(54)# | 0.96+0.56 −0.41 zs | n | $^{29}$ F | | |
| $^{31}$ F | 9 | 22 | 31.06020(570)# | 2 ms# [> 260 ns] | β$^−$ ? | $^{31}$ Ne ? | 5/2+# | |
| $^{31}$ F | 9 | 22 | 31.06020(570)# | 2 ms# [> 260 ns] | β$^−$n ? | $^{30}$ Ne ? | 5/2+# | |
| $^{31}$ F | 9 | 22 | 31.06020(570)# | 2 ms# [> 260 ns] | β$^−$2n ? | $^{29}$ Ne ? | 5/2+# | |
| This table header & footer: view |||||||||
* ↑ $^m$F – Excited nuclear isomer.
* ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
* ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
* 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Modes of decay: EC:Electron capture IT:Isomeric transition n:Neutron emission p:Proton emission
* ↑ Bold symbol as daughter – Daughter product is stable.
* ↑ ( ) spin value – Indicates spin with weak assignment arguments.
* 1 2 3 4 5 6 7 8 9 10 Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.
* ↑ Intermediate product of various CNO cycles in stellar nucleosynthesis as part of the process producing helium from hydrogen
* ↑ Has medicinal uses

## Fluorine-18

Of the unstable nuclides of fluorine, $^{18}$ F has the longest half-life, 109.734(8) min. It decays to $^{18}$ O via β$^+$ decay. For this reason $^{18}$ F is a commercially important source of positrons. Its major value is in the production of the radiopharmaceutical fludeoxyglucose, used in positron emission tomography in medicine.
Fluorine-18 is the lightest unstable nuclide with equal odd numbers of protons and neutrons, having 9 of each. (See also the "magic numbers" discussion of nuclide stability.)

## Fluorine-19

Fluorine-19 is the only stable isotope of fluorine. Its abundance is 100%; no other isotopes of fluorine exist in significant quantities. Its binding energy is 147801.3648(38) keV. Fluorine-19 is NMR-active with a spin of 1/2+, so it is used in fluorine-19 NMR spectroscopy.

## Fluorine-20

Fluorine-20 is an unstable isotope of fluorine. It has a half-life of 11.0062(80) s and decays via beta decay to the stable nuclide $^{20}$ Ne . Its specific radioactivity is 1.8693(14)×10$^{+21}$ Bq/g and has a mean lifetime of 15.879(12) s.

## Fluorine-21

Fluorine-21, as with fluorine-20, is also an unstable isotope of fluorine. It has a half-life of 4.158(20) s. It undergoes beta decay as well, decaying to $^{21}$ Ne , which is a stable nuclide. Its specific activity is 4.781(23)×10$^{+21}$ Bq/g.

## Isomers

Only two nuclear isomers (long-lived excited nuclear states), fluorine-18m and fluorine-26m, have been characterized. The half-life of $^{18m}$ F before it undergoes isomeric transition is 162(7) nanoseconds. This is less than the decay half-life of any of the fluorine radioisotope nuclear ground states except for mass numbers 14–16, 28, and 31. The half-life of $^{26m}$ F is 2.2(1) milliseconds; it decays mainly to its ground state of $^{26}$ F or (rarely, via beta-minus decay) to one of high excited states of $^{26}$ Ne with delayed neutron emission.