Isotopes of boron

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Boron (B) naturally occurs in two isotopes, 10B and 11B, the latter of which makes up about 80% of natural boron. 14 radioisotopes 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.

Standard atomic mass: 10.811(7) u

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

Table[edit]

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 6Be[n 1] (32−)
8B[n 2] 5 3 8.0246072(11) 770(3) ms β+, fission 2 4He 2+
9B 5 4 9.0133288(11) 800(300)×10−21 s
[0.54(21) keV]
p 8Be[n 3] 32
10B 5 5 10.0129370(4) Stable 3+ 19.9(7) 18.929 – 20.386
11B 5 6 11.0093054(4) Stable 32 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[n 4]
13B 5 8 13.0177802(12) 17.33(17) ms β (99.72%) 13C 32
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 32
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[n 5] 5 12 17.04699(18) 5.08(5) ms β, n (63.0%) 16C (32−)
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[n 5] 5 14 19.06373(43)# 2.92(13) ms β 19C (32−)#
  1. ^ Subsequently decays by double proton emission to 4He for a net reaction of 7B → 4He + 31H
  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 → 34He + e
  5. ^ a b Has 2 halo neutrons

Notes[edit]

  • 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 expanded 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[edit]

Boron-10[edit]

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

References[edit]

Notes[edit]

  1. ^ http://www.nucleonica.net/unc.aspx
  2. ^ "2.5.7. Standard and expanded uncertainties". Engineering Statistics Handbook. Retrieved 2010-09-16. 

General references[edit]


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