|Standard atomic weight Ar, standard(F)||18.998403163(6)|
Fluorine (9F) has 18 known isotopes ranging from 13F to 31F (with the exception of 30F) and two isomers (18mF and 26mF). Only fluorine-19 is stable and naturally occurring; therefore, fluorine is a monoisotopic and mononuclidic element, and only artificially produced fluorine isotopes have mass numbers other than 19.
The longest-lived radioisotope is 18F; it has a half-life of 109.739 minutes. 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 14F, whose half-life is 500(60) × 10−24 seconds, corresponding to a spectral linewidth of about 1 MeV.
List of isotopes
|Z||N||Isotopic mass (Da)
[n 2][n 3]
[n 7][n 4]
|Natural abundance (mole fraction)|
|Excitation energy||Normal proportion||Range of variation|
|18F[n 9]||9||9||18.0009373(5)||109.739(9) min||β+ (96.86%)||18O||1+||Trace|
|18mF||1121.36(15) keV||162(7) ns||IT||18F||5+|
|22F||9||13||22.002999(13)||4.23(4) s||β− (89%)||22Ne||(4+)|
|β−, n (11%)||21Ne|
|23F||9||14||23.00353(4)||2.23(14) s||β− (86%)||23Ne||5/2+|
|β−, n (14%)||22Ne|
|24F||9||15||24.00810(10)||384(16) ms||β− (94.1%)||24Ne||3+|
|β−, n (5.9%)||23Ne|
|25F||9||16||25.01217(10)||80(9) ms||β− (76.9%)||25Ne||(5/2+)|
|β−, n (23.1%)||24Ne|
|26F||9||17||26.02002(12)||8.2(9) ms||β− (86.5%)||26Ne||1+|
|β−, n (13.5%)||25Ne|
|26mF||643.4(1) keV||2.2(1) ms||IT (82%)||26F||(4+)|
|β−, n (12%)||25Ne|
|27F||9||18||27.02732(42)||4.9(2) ms||β−, n (77%)||26Ne||5/2+#|
|29F||9||20||29.04310(56)||2.5(3) ms||β−, n (60%)||28Ne||5/2+#|
|31F||9||22||31.06027(59)#||1# ms [>260 ns]||β−||31Ne||5/2+#|
|This table header & footer:|
- mF – 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).
- # – 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.
- The 5/2+ excited state was likely observed, but observation of the ground state is uncertain.
- Has medicinal uses
Of the unstable nuclides of fluorine, 18F has the longest half-life, 109.739 minutes. It has two decay modes, of which the main one is positron emission. For this reason 18F 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.
Like all positron-emitting radioisotopes, 18F also may decay by electron capture. In either case, 18F decays into 18O. The two decay modes do not happen equally frequently however; 96.86% of the decays are by beta plus (positron) emission and 3.14% by electron capture.
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 keV. Fluorine-19 is NMR-active with spin of 1/2, so it is used in fluorine-19 NMR spectroscopy.
Fluorine-20 is one of the more unstable isotopes of fluorine. It has a half-life of 11.13 seconds and undergoes beta decay, transforming into its daughter nuclide 20Ne. Its specific radioactivity is 1.885 × 109 TBq/g and has a lifetime of 15.87 seconds.
Fluorine-21, as with fluorine-20, is also one of unstable isotopes of this element. It has a half-life of 4.158 seconds. It undergoes beta decay as well, which leaves behind a daughter nuclei of 21Ne. Its specific radioactivity is 4.78 × 109 TBq/g.
Only two nuclear isomers (long-lived excited nuclear states), fluorine-18m and fluorine-26m, have been characterized. The half-life of 18mF before gamma ray emission 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 26mF is 2.2(1) milliseconds; it decays mainly to the ground state of 26F or (rarely, via beta-minus decay) to one of high excited states of 26Ne with delayed neutron emission.
- Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
- Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
- Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
- Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
- Charity, R. J. (2 April 2021). "Observation of the Exotic Isotope 13 F Located Four Neutrons beyond the Proton Drip Line". Physical Review Letters. 126 (13): 2501. doi:10.1103/PhysRevLett.126.132501. Retrieved 5 April 2021.
-  F-18 branching ratio for positron emission vs. EC
- National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.