Isotopes of boron

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 for ⁷
B and ⁹
B) while those with mass above 11 mostly become carbon.

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

Isotopes of boron (₅B)

Main isotopes Decay 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)
	[10.806, 10.821][1] 10.81±0.02 (abridged)[2]
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List of isotopes

Nuclide [n 1]	Z	N	Isotopic mass (Da)[3] [n 2][n 3]	Half-life[4] [resonance width]	Decay mode[4] [n 4]	Daughter isotope [n 5]	Spin and parity[4] [n 6][n 7]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion[4]	Range of variation
7 B	5	2	7.029712(27)	570(14) ys [801(20) keV]	p	6 Be[n 8]	(3/2−)
8 B[n 9][n 10]	5	3	8.0246073(11)	771.9(9) ms	β+α	4 He	2+
8m B	10624(8) keV						0+
9 B	5	4	9.0133296(10)	800(300) zs	p	8 Be[n 11]	3/2−
10 B[n 12]	5	5	10.012936862(16)	Stable			3+	[0.189, 0.204][5]
11 B	5	6	11.009305167(13)	Stable			3/2−	[0.796, 0.811][5]
11m B	12560(9) keV						1/2+, (3/2+)
12 B	5	7	12.0143526(14)	20.20(2) ms	β− (99.40(2)%)	12 C	1+
					β−α (0.60(2)%)	8 Be[n 13]
13 B	5	8	13.0177800(11)	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)	12.36(29) ms	β− (93.96(23)%)	14 C	2−
					β−n (6.04(23)%)	13 C
					β−2n ?[n 14]	12 C ?
14m B	17065(29) keV			4.15(1.90) zs	IT ?[n 14]		0+
15 B	5	10	15.031087(23)	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)	> 4.6 zs	n ?[n 14]	15 B ?	0−
17 B[n 15]	5	12	17.04693(22)	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)	< 26 ns	n	17 B	(2−)
19 B[n 16]	5	14	19.06417(56)	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[6]	5	15	20.07451(59)	> 912.4 ys	n	19 B	(1−, 2−)
21 B[6]	5	16	21.08415(60)	> 760 ys	2n	19 B	(3/2−)
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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 ⁴
   He for a net reaction of ⁷
   B → ⁴
   He + 3 ¹
   H
9. Has 1 halo proton
10. Intermediate product of a branch of proton–proton chain in stellar nucleosynthesis as part of the process converting hydrogen to helium
11. Immediately decays into two α particles, for a net reaction of ⁹
    B → 2 ⁴
    He + ¹
    H
12. One of the few stable odd-odd nuclei
13. Immediately decays into two α particles, for a net reaction of ¹²
    B → 3 ⁴
    He +  e⁻
14. Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.
15. Has 2 halo neutrons
16. 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.^[7]

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,^[8] and are an important background to dark matter direct detection experiments.^[9] 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

• Isotopes of carbon
• Isotopes of beryllium
• Isotopes of helium