See also: List of individual Erbium isotopes (and general data sources).
General data
Name of the isotope:Erbium-156; Er-156Symbol:156Er or 15668ErMass number A:156 (= number of nucleons)Atomic number Z:68 (= number of protons)Neutrons N:88Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.2941176470588 (= neutron-proton ratio)Neutron excess (N-Z):20Isotopic mass:155.931066(26) u (atomic weight of Erbium-156)Nuclide mass:155.8937659 u (calculated nuclear mass without electrons)Mass excess:-64.21161 MeVMass defect:1.363548784 u (per nucleus)Nuclear binding energy:1270.137511 MeV (per nucleus) 8.14190712 MeV (average binding energy per nucleon)Separation energy:SN = 10.074(25) MeV (first neutron) SP = 5.46(3) MeV (first proton)Half-life:19.5(10) minDecay constant λ:0.00059243348765807 s-1Specific activity α:2.288009660380 × 10+18 Bq g-1 61838098.929208 Ci g-1Spin and parity: (nuclear angular momentum)0+Charge radius:5.1429(285) femtometer fmYear of discovery:1967
Radioactive Decay
Half-life T½ = 19.5(10) min (minutes) respectively 1.170 × 103 seconds s.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 88) and isobaric (same nucleon number A = 156) with Erbium-156. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
