Boron-12

Properties and data of the isotope ¹²B.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Boron-12 is a radioisotope of the chemical element boron, which has 7 neutrons in its atomic nucleus in addition to the element-specific 5 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 12. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹²B is exclusively for academic purposes.

The discovery of the isotope was reported in 1935; boron-12 was produced by bombarding boron-11 with a beam of deuterons (hydrogen-2 nuclei, ²H, 0.5 MeV) [1]:

¹¹B(d,p)¹²B.

Another nuclear reaction for the synthesis of boron-12 dates back to 2016 [2]:

¹²C(n,p)¹²B.

General data

Name of the isotope:Boron-12; B-12Symbol:¹²B or 125BMass number A:12 (= number of nucleons)Atomic number Z:5 (= number of protons)Neutrons N:7Isotopic mass:12.0143526(14) u (atomic weight of Boron-12)Nuclide mass:12.0116097 u (calculated nuclear mass without electrons)Mass excess:13.36936 MeVMass defect:0.085426971999999 u (per nucleus)Nuclear binding energy:79.57471186 MeV (per nucleus)
6.63122599 MeV (average binding energy per nucleon)Separation energy:S_N = 3.3696(13) MeV (first neutron)
S_P = 14.0967(13) MeV (first proton)Half-life:20.20(2) msDecay constant λ:34.314216859403 s^-1Specific activity α:1.722042061881 × 10⁺²⁴ Bq g^-1
46541677348141 Ci g^-1Spin and parity:
(nuclear angular momentum)1+Isobaric spin: 1Magnetic dipole moment:μ(μ_N) = +1.003(1)Quadrupole moment Q:0.0132(3) barn (100 fm²)Nuclear g-factor:g_l = 1.003Mirror nucleus:Nitrogen-12Year of discovery:1935

Radioactive Decay

Half-life T_½ = 20.20(2) ms respectively 2.020 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹²C	99.40(2) %	13.3694(13) MeV
β^-, α	⁸Be	0.60(2) %

Parent Nuclides

Direct parent isotope is: ¹²Be.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 7) and isobaric (same nucleon number A = 12) with Boron-12. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 7	Isobar A = 12
2	⁹He
3	¹⁰Li	¹²Li
4	¹¹Be	¹²Be
5	¹²B	¹²B
6	¹³C	¹²C
7	¹⁴N	¹²N
8	¹⁵O	¹²O
9	¹⁶F
10	¹⁷Ne
11	¹⁸Na
12	¹⁹Mg

External data and identifiers

Adopted Levels, Gammas:NuDat 12B

Literature and References

[1] - H. R. Crane, L. A. Delsasso, W. A. Fowler, C. C. Lauritsen:
The Emission of Negative Electrons from Boron Bombarded by Deuterons.
In: Physical Review, 47, 887, (1935), DOI 10.1103/PhysRev.47.887.

[2] - P. Žugec, N. Colonna, D. Bosnar et al.:
Integral measurement of the ¹²C(n, p)¹²B reaction up to 10 GeV.
In: The European Physical Journal A, 52, 101, (2016), DOI 10.1140/epja/i2016-16101-7.