See also: List of individual Thorium isotopes (and general data sources).
General data
Name of the isotope:Thorium-227; Th-227Other names:Radioactinium. Radio-ActiniumSymbol:227Th or 22790ThMass number A:227 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:137Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.5222222222222 (= neutron-proton ratio)Neutron excess (N-Z):47Isotopic mass:227.0277025(22) u (atomic weight of Thorium-227)Nuclide mass:226.9783367 u (calculated nuclear mass without electrons)Mass excess:25.80471 MeVMass defect:1.863643872 u (per nucleus)Nuclear binding energy:1735.9730849 MeV (per nucleus) 7.64745852 MeV (average binding energy per nucleon)Separation energy:SN = 5.464(5) MeV (first neutron) SP = 5.793(3) MeV (first proton)Cross section: σ(n.f) = 200(20) b (gap cross-section)Half-life:18.697(7) dDecay constant λ:4.29081500349 × 10-7 s-1Specific activity α:1.138182329364 × 10+15 Bq g-1 30761.684577419 Ci g-1Spin and parity: (nuclear angular momentum)(1/2+)Charge radius:5.7404(165) femtometer fmYear of discovery:1906
Radioactive Decay
Half-life T½ = 18.697(7) d respectively 1.6154208 × 106 seconds s.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 137) and isobaric (same nucleon number A = 227) with Thorium-227. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
[1] - Viviana Frantellizzi, Laura Cosma, Gabriele Brunotti et al.: Targeted Alpha Therapy with Thorium-227. In: Cancer Biotherapy & Radiopharmaceuticals, (2020), DOI 10.1089/cbr.2019.3105.
