Isotopes of boron

Boron (B) naturally occurs in two 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)	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	6Be	(​3⁄2−)
8B	5	3	8.0246072(11)	770(3) ms	β+, α	2 4He	2+
9B	5	4	9.0133288(11)	800(300)×10−21 s [0.54(21) keV]	p	8Be	​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%)	12C	1+
					β−, α (1.6%)	8Be
13B	5	8	13.0177802(12)	17.33(17) ms	β− (99.72%)	13C	​3⁄2−
					β−, n (0.279%)	12C
14B	5	9	14.025404(23)	12.5(5) ms	β− (93.96%)	14C	2−
					β−, n (6.04%)	13C
15B	5	10	15.031103(24)	9.87(7) ms	β−, n (93.6%)	14C	​3⁄2−
					β− (6.0%)	15C
					β−, 2n (0.40%)	13C
16B	5	11	16.03981(6)	<190×10−12 s [<0.1 MeV]	n	15B	0−
17B	5	12	17.04699(18)	5.08(5) ms	β−, n (63.0%)	16C	(​3⁄2−)
					β− (22.1%)	17C
					β−, 2n (11.0%)	15C
					β−, 3n (3.5%)	14C
					β−, 4n (0.40%)	13C
18B	5	13	18.05617(86)#	<26 ns	n	17B	(4−)#
19B	5	14	19.06373(43)#	2.92(13) ms	β−	19C	(​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.

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:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

Isotopes of beryllium	Isotopes of boron	Isotopes of carbon
Table of nuclides