Boron-12

Properties and data of the isotope ¹²B.

Content

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	99.4 %	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.