Isotopes of fluorine

Fluorine (9F) has 18 known isotopes ranging from 13
F
 to 31
F
 (with the exception of 30
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.

Isotopes of fluorine (9F)
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
18F trace 109.734 min β+ 18O
19F 100% stable
Standard atomic weight Ar°(F)
  • 18.998403162±0.000000005
  • 18.998±0.001 (abridged)[2][3]

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.

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

Fluorine-18
Main article: 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.)[8]

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.[4] The half-life of 18m
F
 before it undergoes isomeric transition is 162(7) nanoseconds.[4] 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. [9] 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.[4]

References
  1. Chisté & Bé 2011.
  2. "Standard Atomic Weights: Fluorine". CIAAW. 2021.
  3. Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  5. Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
    Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  6. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  7. 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. Bibcode:2021PhRvL.126m2501C. doi:10.1103/PhysRevLett.126.132501. OSTI 1773500. PMID 33861136. S2CID 233259561. Retrieved 5 April 2021.
  8. National Nuclear Data Center. "NuDat 2.x database". Brookhaven National Laboratory.
  9. 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.

Sources
  • Chisté, V.; Bé, M. M. (2011). "F-18" (PDF). In Bé, M. M.; Coursol, N.; Duchemin, B.; Lagoutine, F.; et al. (eds.). Table de radionucléides (Report). CEA (Commissariat à l'énergie atomique et aux énergies alternatives), LIST, LNE-LNHB (Laboratoire National Henri Becquerel/Commissariat à l'Energie Atomique). Archived from the original (PDF) on 11 August 2020. Retrieved 15 June 2011.
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