Oxygen-12

Properties and data of the isotope ¹²O.

Content

General data

Name of the isotope:Oxygen-12; O-12Symbol:¹²O or 128OMass number A:12 (= number of nucleons)Atomic number Z:8 (= number of protons)Neutrons N:4Isotopic mass:12.034368(13) u (atomic weight of Oxygen-12)Nuclide mass:12.0299794 u (calculated nuclear mass without electrons)Mass excess:32.01359 MeVMass defect:0.062891919999998 u (per nucleus)Nuclear binding energy:58.58344613 MeV (per nucleus)
4.88195384 MeV (average binding energy per nucleon)Separation energy:S_N = 23.797(61) MeV (first neutron)Half-life:6.3(30) × 10^-21 sDecay constant λ:1.093292082902 × 10⁺²⁰ s^-1Specific activity α:5.486632436908 × 10⁺⁴² Bq g^-1
1.482873631596 × 10⁺³² Ci g^-1Spin and parity:
(nuclear angular momentum)0+Isobaric spin: 2Mirror nucleus:Beryllium-12Year of discovery:1978

Radioactive Decay

Half-life T_½ = 6.3(30) × 10^-21 s respectively 6.34 × 10^-21 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
2p	¹⁰C		14.675(12) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 4) and isobaric (same nucleon number A = 12) with Oxygen-12. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.