See also: List of individual Thorium isotopes (and general data sources).
General data
Name of the isotope:Thorium-238; Th-238Symbol:238Th or 23890ThMass number A:238 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:148Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.6444444444444 (= neutron-proton ratio)Neutron excess (N-Z):58Isotopic mass:238.05639(30) u (atomic weight of Thorium-238)Nuclide mass:238.0070242 u (calculated nuclear mass without electrons)Mass excess:52.52695 MeVMass defect:1.930270448 u (per nucleus)Nuclear binding energy:1798.03534069 MeV (per nucleus) 7.55477034 MeV (average binding energy per nucleon)Separation energy:SN = 5.50(28) MeV (first neutron) SP = 8.78(49) MeV (first proton)Half-life:9.4(20) minDecay constant λ:0.0012289843626949 s-1Specific activity α:3.108976332871 × 10+18 Bq g-1 84026387.3749 Ci g-1Spin and parity: (nuclear angular momentum)0+Year of discovery:1999
Radioactive Decay
Half-life T½ = 9.4(20) min (minutes) respectively 5.64 × 102 seconds s.
Decay mode
Daughter
Probability
Decay energy
γ energy (intensity)
β-
238Pa
100 %
1.63(28) MeV
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 148) and isobaric (same nucleon number A = 238) with Thorium-238. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
