Isotopes of boron

Boron (B) 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, with the least stable isotope being ⁷B, with a half-life of 150 yoctoseconds (ys). 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.

Relative atomic mass: 10.811(7)

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

Table

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)[1]	daughter isotope(s)	nuclear spin	representative isotopic composition (mole percent)	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 [n 1]	( ^3⁄2−)
^8B[n 2]	5	3	8.0246072(11)	770(3) ms	β^+, α	2 4 He	2+
^9B	5	4	9.0133288(11)	800(300)×10^−21 s [0.54(21) keV]	p	8 Be [n 3]	^3⁄2−
^10B	5	5	10.0129370(4)	Stable			3+	19.9(7)	18.929–20.386
^11B	5	6	11.0093054(4)	Stable			^3⁄2−	80.1(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 [n 4]
^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[n 5]	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[n 5]	5	14	19.06373(43)#	2.92(13) ms	β^−	19 C	( ^3⁄2−)#

1. Subsequently decays by double proton emission to ⁴He for a net reaction of ⁷B → ⁴He + 3 ¹H
2. Has 1 halo proton
3. immediately decays into two α particles, for a net reaction of ⁹B → 2 ⁴He + ¹H
4. Immediately decays into two α particles, for a net reaction of ¹²B → 3 ⁴He +  e⁻
5. Has 2 halo neutrons

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.^[2]
• 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.

Applications

Boron-10

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

References

Notes

1. "Universal Nuclide Chart". nucleonica. (registration required (help)).
2. "2.5.7. Standard and expanded uncertainties". Engineering Statistics Handbook. Retrieved 2010-09-16.

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.
• 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.