Thorium-238

Properties and data of the isotope ²³⁸Th.

Content

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:148Isotopic 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:S_N = 5.50(28) MeV (first neutron)
S_P = 8.78(49) MeV (first proton)Half-life:9.4(20) minDecay constant λ:0.0012289843626949 s^-1Specific activity α:3.109713002860 × 10⁺¹⁸ Bq g^-1
84046297.374614 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1999

Radioactive Decay

Half-life T_½ = 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.

OZ	Isotone N = 148	Isobar A = 238
90	²³⁸Th	²³⁸Th
91	²³⁹Pa	²³⁸Pa
92	²⁴⁰U	²³⁸U
93	²⁴¹Np	²³⁸Np
94	²⁴²Pu	²³⁸Pu
95	²⁴³Am	²³⁸Am
96	²⁴⁴Cm	²³⁸Cm
97	²⁴⁵Bk	²³⁸Bk
98	²⁴⁶Cf	²³⁸Cf
99	²⁴⁷Es
100	²⁴⁸Fm
101	²⁴⁹Md
102	²⁵⁰No
103	²⁵¹Lr