Isotopes of boron

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Boron (5B) naturally occurs as isotopes 10
B and 11
B, 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 8
B, with a half-life of only 771.9(9) ms and 12
B with a half-life of 20.20(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 while those with mass above 11 mostly become carbon.

Quick facts Main isotopes, Decay ...
Isotopes of boron (5B)
Main isotopes[1] Decay
Isotope 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)
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List of isotopes

More information Nuclide, Z ...
Nuclide
 Z N Isotopic mass (Da)[4]
[n 1]		 Discovery
year[5]		 Half-life[1]

[resonance width]		 Decay
mode[1]
[n 2]		 Daughter
isotope
[n 3]		 Spin and
parity[1]
[n 4][n 5]		 Natural abundance (mole fraction)
Normal proportion[1] Range of variation
7
B		 5  2 7.029712(27) 1967 570(14) ys
[801(20) keV]		 p 6
Be[n 6]		 (3/2−)
8
B[n 7][n 8]		 5  3 8.0246073(11) 1950 771.9(9) ms β+ 8
Be[n 9]		 2+
9
B		 5  4 9.0133296(10) 1940 800(300) zs p 8
Be[n 10]		 3/2−
10
B[n 11]		 5  5 10.012936862(16) 1920 Stable 3+ [0.189, 0.204][6]
11
B		 5  6 11.009305167(13) 1920 Stable 3/2− [0.796, 0.811][6]
12
B		 5  7 12.0143526(14) 1935 20.20(2) ms β− (99.40(2)%) 12
C		 1+
β−α (0.60(2)%) 8
Be[n 12]
13
B		 5  8 13.0177800(11) 1956 17.16(18) ms β− (99.734(36)%) 13
C		 3/2−
β−n (0.266(36)%) 12
C
14
B		 5  9 14.025404(23) 1966 12.36(29) ms β− (93.96(23)%) 14
C		 2−
β−n (6.04(23)%) 13
C
β−2n ?[n 13] 12
C ?
15
B		 5 10 15.031087(23) 1966 10.18(35) ms β−n (98.7(1.0)%) 14
C		 3/2−
β− (< 1.3%) 15
C
β−2n (< 1.5%) 13
C
16
B		 5 11 16.039841(26) 2000 > 4.6 zs n ?[n 13] 15
B ?		 0−
17
B[n 14]		 5 12 17.04693(22) 1973 5.08(5) ms β−n (63(1)%) 16
C		 (3/2−)
β− (21.1(2.4)%) 17
C
β−2n (12(2)%) 15
C
β−3n (3.5(7)%) 14
C
β−4n (0.4(3)%) 13
C
18
B		 5 13 18.05560(22) 2010 < 26 ns n 17
B		 (2−)
19
B[n 15]		 5 14 19.06417(56) 1984 2.92(13) ms β−n (71(9)%) 18
C		 (3/2−)
β−2n (17(5)%) 17
C
β−3n (< 9.1%) 16
C
β− (> 2.9%) 19
C
20
B[7]		 5 15 20.07451(59) 2018 > 912.4 ys n 19
B		 (1−, 2−)
21
B[7]		 5 16 21.08415(60) 2018 > 760 ys 2n 19
B		 (3/2−)
This table header & footer:
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  1. [1]
    ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  2. [2]
    Modes of decay:
    n:Neutron emission
    p:Proton emission
  3. [3]
    Bold symbol as daughter – Daughter product is stable.
  4. [4]
    ( ) spin value – Indicates spin with weak assignment arguments.
  5. [5]
    # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  6. [6]
    Subsequently decays by double proton emission to 4
    He     for a net reaction of 7
    B     → 4
    He     + 3 1
    H
  7. [7]
    Has 1 halo proton
  8. [8]
    Intermediate product of a branch of proton–proton chain in stellar nucleosynthesis as part of the process converting hydrogen to helium
  9. [9]
    Immediately decays into two α particles, for a net reaction of 8
    B     → 2 4
    He     + e+
  10. [10]
    Immediately decays into two α particles, for a net reaction of 9
    B     → 2 4
    He     + 1
    H
  11. [11]
    One of the few stable odd-odd nuclei
  12. [12]
    Immediately decays into two α particles, for a net reaction of 12
    B     → 3 4
    He     +  e−
  13. [13]
    Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.
  14. [14]
    Has 2 halo neutrons
  15. [15]
    Has 4 halo neutrons

Boron-8

Boron-8 is an isotope of boron that undergoes β+ decay to beryllium-8 with a half-life of 771.9(9) ms. It is the strongest candidate for a halo nucleus with a loosely-bound proton, in contrast to neutron halo nuclei such as lithium-11.[8]

Although boron-8 beta decay neutrinos from the Sun make up only about 80 ppm of the total solar neutrino flux, they have a higher energy centered around 10 MeV,[9] and are an important background to dark matter direct detection experiments.[10] 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.

See also

Daughter products other than boron

References

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