Thorium-227

Properties and data of the isotope ²²⁷Th.

Content

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

General data

Name of the isotope:Thorium-227; Th-227Other names:RadioactiniumSymbol:²²⁷Th or 22790ThMass number A:227 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:137Isotopic 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:S_N = 5.464(5) MeV (first neutron)
S_P = 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:1.138321249118 × 10⁺¹⁵ Bq g^-1
30765.439165357 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Charge radius:5.7404(165) femtometer fmYear of discovery:1906

Radioactive Decay

Half-life T_½ = 18.697(7) d respectively 1.6154208 × 10⁶ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²²³Ra	100 %	6.1466(1) MeV

Parent Nuclides

Direct parent isotopes are: ²³¹U, ²²⁷Ac, ²²⁷Pa.

Isotones and Isobars

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.

OZ	Isotone N = 137	Isobar A = 227
82	²¹⁹Pb
83	²²⁰Bi
84	²²¹Po	²²⁷Po
85	²²²At	²²⁷At
86	²²³Rn	²²⁷Rn
87	²²⁴Fr	²²⁷Fr
88	²²⁵Ra	²²⁷Ra
89	²²⁶Ac	²²⁷Ac
90	²²⁷Th	²²⁷Th
91	²²⁸Pa	²²⁷Pa
92	²²⁹U	²²⁷U
93	²³⁰Np	²²⁷Np
94	²³¹Pu
95	²³²Am
96	²³³Cm
97	²³⁴Bk

External data and identifiers

Adopted Levels, Gammas:NuDat 227Th

Literature and References

[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.