Isotopes of fluorine

Although fluorine (F) has 18 known isotopes from ¹⁴F to ³¹F and one isomer (^18mF), only one of these isotopes is stable, that is, fluorine-19; as such, it is a monoisotopic element. The longest-lived radioisotope is ¹⁸F with a half-life of 109.771 minutes. All other isotopes have half-lives under a minute, the majority under a second, making fluorine a mononuclidic element as well. The least stable isotope is ¹⁵F, whose half-life is 4.1 x 10⁻²² seconds, corresponding to a spectral linewidth of about 1 MeV. Only ¹⁴F has an unknown half-life.

Relative atomic mass: 18.9984032(5)

Fluorine-18

The nuclide ¹⁸F is the radionuclide of fluorine with the longest half-life, 109.771 minutes, allowing it to serve commercially as an important source of positrons. Its major use is for the production of the radiopharmaceutical fludeoxyglucose for positron emission tomography scanning in medicine.

Like all positron-emitting radioisotopes, ¹⁸F also has a probability to decay by electron capture. In this case, ¹⁸F decays into ¹⁸O, 96.86 (19)% of the time by beta plus (positron) emission and 3.14 (19)% by electron capture.^[1]

It is the lightest unstable nuclide with equal odd numbers of protons and neutrons, 9 of each. (See also the "magic numbers" discussion of nuclide stability.)^[2]

Fluorine-19

Fluorine-19, 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, so it is used in fluorine-19 NMR spectroscopy.

Fluorine-20

Fluorine-20, is one of the more unstable isotopes of fluorine. It has a half-life of 11.07 seconds and undergoes beta decay, transforming into its daughter nuclide ²⁰Ne. Its specific radioactivity is 1.885 x 10⁹ TBq/g and has a lifetime of 15.87 seconds.

Fluorine-21

Fluorine-21, as with fluorine-20, is also one of the most 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 x 10⁹ TBq/g.

Isomers

Only one nuclear isomer (long-lived excited nuclear state), fluorine-18m, has been characterized.^[3] Its half-life before gamma ray emission is 160 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.^[3]

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[4]	daughter isotope(s)[n 1]	nuclear spin	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)
	excitation energy
^14F	9	5	14.03506(43)#		p	^13O	2-#
^15F	9	6	15.01801(14)	410(60)×10^−22 s [1.0(2) MeV]	p	^14O	(1/2+)
^16F	9	7	16.011466(9)	11(6)×10^−21 s [40(20) keV]	p	^15O	0−
^17F	9	8	17.00209524(27)	64.49(16) s	β^+	^17O	5/2+
^18F[n 2]	9	9	18.0009380(6)	109.771(20) min	β^+	^18O	1+
^18mF	1121.36(15) keV			162(7) ns			5+
^19F	9	10	18.99840322(7)	Stable			1/2+	1.0000
^20F	9	11	19.99998132(8)	11.163(8) s	β^−	^20Ne	2+
^21F	9	12	20.9999490(19)	4.158(20) s	β^−	^21Ne	5/2+
^22F	9	13	22.002999(13)	4.23(4) s	β^− (89.0%)	^22Ne	4+,(3+)
					β^−, n (11.0%)	^21Ne
^23F	9	14	23.00357(9)	2.23(14) s	β^− (86.0%)	^23Ne	5/2+
					β^−, n (14.0%)	^22Ne
^24F	9	15	24.00812(8)	400(50) ms	β^− (94.1%)	^24Ne	(1,2,3)+
					β^−, n (5.9%)	^23Ne
^25F	9	16	25.01210(11)	50(6) ms	β^− (76.0%)	^25Ne	(5/2+)#
					β^−, n (24.0%)	^24Ne
^26F	9	17	26.01962(18)	9.6(8) ms	β^− (68.0%)	^26Ne	1+
					β^−, n (32.0%)	^25Ne
^27F	9	18	27.02676(40)	4.9(2) ms	β^−	^27Ne	5/2+#
^28F	9	19	28.03567(55)#	<40 ns	n	^27F
^29F	9	20	29.04326(62)#	2.6(3) ms	β^−	^29Ne	5/2+#
^30F	9	21	30.05250(64)#	<260 ns
^31F	9	22	31.06043(64)#	1# ms [>260 ns]			5/2+#

1. Bold for stable isotopes
2. Has medicinal uses

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.

References

• Isotope masses from:
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
• Isotopic compositions and standard atomic masses from:
  • J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
  • M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051. Lay summary.
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
  • G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in: |access-date= (help)
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

1. F-18 branching ratio for positron emission vs. EC
2. National Nuclear Data Center. "NuDat 2.1 database – Fluorine-18". Brookhaven National Laboratory. Retrieved 19 July 2014.
3. Audi, G.; Wapstra, A. H.; Thibault, C.; Blachot, J.; Bersillon, O. (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
4. "Universal Nuclide Chart". nucleonica. (registration required (help)).

External links

• Information on Fluorine-21 from Wolframalpha.com
• Information on Fluorine-20 from Wolframalpha.com