See also: List of individual Nobelium isotopes (and general data sources).
General data
Name of the isotope:Nobelium-251m; No-251mSymbol:251mNo or 251m102NoMass number A:251 (= number of nucleons)Atomic number Z:102 (= number of protons)Neutrons N:149Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4607843137255 (= neutron-proton ratio)Neutron excess (N-Z):47Excitation energy:106(6) keVIsotopic mass:251.08894(12) u (atomic weight of Nobelium-251m)Nuclide mass:251.0329933 u (calculated nuclear mass without electrons)Mass excess:82.84708 MeVMass defect:2.000285748 u (per nucleus)Nuclear binding energy:1863.25417255 MeV (per nucleus) 7.4233234 MeV (average binding energy per nucleon)Half-life:1.02(3) sDecay constant λ:0.6795560593725 s-1Specific activity α:1.629853646222 × 10+21 Bq g-1 44050098546.562 Ci g-1Spin and parity: (nuclear angular momentum)(1/2+)
Radioactive Decay
Half-life T½ = 1.02(3) s.
Decay mode
Daughter
Probability
Decay energy
γ energy (intensity)
α
247Fm
ca. 100 %
Nuclear Isomers
Nuclear isomers or excited states with the activation energy in keV related to the ground state.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 149) and isobaric (same nucleon number A = 251) with Nobelium-251m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
