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.

Isotopes of boron (₅B)

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

Nuclide	Z	N	Isotopic mass (Da)	Half-life [resonance width]	Decay mode	Daughter isotope	Spin and parity	Natural abundance (mole fraction)
	Excitation energy							Normal proportion	Range of variation
^7 B	5	2	7.029712(27)	570(14) ys [801(20) keV]	p	^6 Be	(3/2−)
^8 B	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	3/2−
^10 B	5	5	10.012936862(16)	Stable			3+	[0.189, 0.204]
^11 B	5	6	11.009305167(13)	Stable			3/2−	[0.796, 0.811]
^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
^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 ?	^12 C ?
^14m B	17065(29) keV			4.15(1.90) zs	IT ?		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 ?	^15 B ?	0−
^17 B	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	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	5	15	20.07451(59)	> 912.4 ys	n	^19 B	(1−, 2−)
^21 B	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.

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, and are an important background to dark matter direct detection experiments. 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