Isotopes of boron

Boron (5B) naturally occurs as isotopes 10B and 11B, the latter of which makes up about 80% of natural boron. There are 13 radioisotopes that have been discovered, with mass numbers from 7 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.
Main isotopes of boron (5B)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
10B [0.189, 0.204] stable[1]
11B [0.796, 0.811] stable[1]
Standard atomic weight Ar, standard(B)[10.806, 10.821] conventional: 10.81[2][3]

List of isotopes
Nuclide[4]
[n 1]		 Z N Isotopic mass (Da)[5]
[n 2][n 3]		 Half-life

[resonance width]		 Decay
mode
[n 4]		 Daughter
isotope
[n 5]		 Spin and
parity
[n 6][n 7]		 Natural abundance (mole fraction)
Excitation energy Normal proportion Range of variation
7B 5  2 7.029712000±0.000027000 570±14 ys [801(20) keV] p 6
Be
[n 8]		 (3/2−)
8B[n 9] 5  3 8.024607315±0.000001073 771.9±0.9 ms β+, α 2 4
He
 2+
9B 5  4 9.013329645±0.000000969 800±300 zs [0.54(21) keV] p, α 2 4
He
 3/2−
10B[n 10] 5  5 10.012936862±0.000000016 Stable 3+ [0.189, 0.204][6]
11B 5  6 11.009305166±0.000000013 Stable 3/2− [0.796, 0.811][6]
12B 5  7 12.014352638±0.000001418 20.20±0.02 ms β− (98.4%) 12
C
 1+
β−, α (1.6%) 8
Be
[n 11]
13B 5  8 13.017779981±0.000001073 17.16±0.18 ms β− (99.72%) 13
C
 3/2−
β−, n (0.28%) 12
C
14B 5  9 14.025404010±0.000022773 12.36±0.29 ms β− (93.96%) 14
C
 2−
β−, n (6.04%) 13
C
15B 5 10 15.031087023±0.000022575 10.18±0.35 ms β−, n (93.6%) 14
C
 3/2−
β− (6.0%) 15
C
β−, 2n (0.4%) 13
C
16B 5 11 16.039841045±0.000026373 >4.6 zs n 15
B
 0−
17B[n 12] 5 12 17.046931399±0.000219114 5.08±0.05 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 (0.4%) 13
C
18B 5 13 18.055601683±0.000219180 <26 ns n 17
B
 (2−)
19B[n 12] 5 14 19.064166000±0.000564000 2.92±0.13 ms β−, n (71%) 18
C
 3/2−#
β−, 2n (17%) 17
C
β− (12%) 19
C
20B[7] 5 15 20.074505644±0.000586538 >912.4 ys n 19
B
 (1−, 2−)
21B[7] 5 16 21.084147485±0.000599750 <760 ys [2.47(19) MeV] 2n 19
B
 (3/2−)#
This table header & footer:
  1. mB – Excited nuclear isomer.
  2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. Modes of decay:
    n:Neutron emission
    p:Proton emission
  5. Bold symbol as daughter – Daughter product is stable.
  6. ( ) spin value – Indicates spin with weak assignment arguments.
  7. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  8. Subsequently decays by double proton emission to 4He for a net reaction of 7B → 4He + 3 1H
  9. Has 1 halo proton
  10. One of the few stable odd-odd nuclei
  11. Immediately decays into two α particles, for a net reaction of 12B → 3 4He +  e−
  12. Has 2 halo neutrons
  • Neutrinos from boron-8 beta decays within the sun are an important background to dark matter direct detection experiments.[8] 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 as an experimental treatment of some brain cancers.

References
  1. "Atomic Weight of Boron". CIAAW. Retrieved 2021-10-26.
  2. "Standard Atomic Weights: Boron". CIAAW. 2009.
  3. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
  4. Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
    Kondev, F.G.; Wang, M.; Huang, W.J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  5. Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  6. "Atomic Weight of Boron". CIAAW.
  7. Leblond, S.; et al. (2018). "First observation of 20B and 21B". Physical Review Letters. 121 (26): 262502–1–262502–6. arXiv:1901.00455. doi:10.1103/PhysRevLett.121.262502. PMID 30636115.
  8. Cerdeno, David G.; Fairbairn, Malcolm; Jubb, Thomas; Machado, Pedro; Vincent, Aaron C.; Boehm, Celine (2016). "Physics from solar neutrinos in dark matter direct detection experiments". JHEP. 2016 (5): 118. arXiv:1604.01025. Bibcode:2016JHEP...05..118C. doi:10.1007/JHEP05(2016)118.
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