Isotopes of boron

Isotopes of boron (₅B)

Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 8B synth 771.9 ms β+ 8Be 10B [18.9%, 20.4%] stable 11B [79.6%, 81.1%] stable
Standard atomic weight Ar°(B)
	[10.806, 10.821] 10.81±0.02 (abridged)

Boron (₅B) naturally occurs as isotopes ¹⁰B and ¹¹B, the latter of which makes up about 80% of natural boron. There are 14 radioisotopes that have been discovered, with mass numbers from 6 to 21, all with short half-lives, the longest being that of ⁸B, with a half-life of only 770 milliseconds (ms) and ¹²B with a half-life of 20.2 ms. All other isotopes have half-lives shorter than 17.35 ms. Those isotopes with mass below 10 decay into helium (via short-lived isotopes of beryllium for ⁷B and ⁹B) while those with mass above 11 mostly become carbon.

A chart showing the abundances of the naturally occurring isotopes of boron.

List of isotopes

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life [resonance width]	decay mode(s)	daughter isotope(s)	nuclear spin and parity	representative isotopic composition (mole fraction)	range of natural variation (mole percent)
6B	5	1	6.04681(75)#
7B	5	2	7.02992(8)	350(50) × 10−24 s [1.4(2) MeV]	p	6 Be	(⁠3/2⁠−)
8B	5	3	8.0246072(11)	770(3) ms	β+, α	2 4 He	2+
9B	5	4	9.0133288(11)	80(30) × 10−21 s [0.54(21) keV]	p, α	8 Be	3⁄2−
10B	5	5	10.0129370(4)	Stable			3+	0.199(7)	18.929–20.386
11B	5	6	11.0093054(4)	Stable			⁠3/2⁠−	0.801(7)	79.614–81.071
12B	5	7	12.0143521(15)	20.20(2) ms	β− (98.4%)	12 C	1+
					β−, α (1.6%)	8 Be
13B	5	8	13.0177802(12)	17.33(17) ms	β− (99.72%)	13 C	⁠3/2⁠−
					β−, n (0.279%)	12 C
14B	5	9	14.025404(23)	12.5(5) ms	β− (93.96%)	14 C	2−
					β−, n (6.04%)	13 C
15B	5	10	15.031103(24)	9.87(7) ms	β−, n (93.6%)	14 C	⁠3/2⁠−
					β− (6.0%)	15 C
					β−, 2n (0.40%)	13 C
16B	5	11	16.03981(6)	< 190 × 10−12 s [< 0.1 MeV]	n	15 B	0−
17B	5	12	17.04699(18)	5.08(5) ms	β−, n (63.0%)	16 C	(⁠3/2⁠−)
					β− (22.1%)	17 C
					β−, 2n (11.0%)	15 C
					β−, 3n (3.5%)	14 C
					β−, 4n (0.40%)	13 C
18B	5	13	18.05617(86)#	< 26 ns	n	17 B	(4−)#
19B	5	14	19.06373(43)#	2.92(13) ms	β−	19 C	(⁠3/2⁠−)#

Notes

• The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
• Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the given mass and composition can occur.
• 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 folical uncertainties.
• Nuclide masses are given by IUPAP Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants (SUNAMCO).
• Isotope abundances are given by IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW).
• Neutrinos from Boron-8 beta decays within the sun are an important background to dark matter direct detection experiments. They are the first component of the neutrino floor that dark matter direct detection experiments are expected to eventually encounter.

Applications

Boron-10

Boron-10 is used in boron neutron capture therapy (BNCT) as an experimental treatment of some brain cancers.

References

General 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. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
• 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. {{cite journal}}: Unknown parameter |laysummary= ignored (help)
• 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. Archived from the original (PDF) on 2008-09-23. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved 23 February 2017.
  • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9. {{cite book}}: Unknown parameter |nopp= ignored (|no-pp= suggested) (help)