Thorium-212

Properties and data of the isotope ²¹²Th.

Contents

See also: List of individual Thorium isotopes (and general data sources).

General data

Name of the isotope:Thorium-212; Th-212Symbol:²¹²Th or 21290ThMass number A:212 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:122Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.3555555555556 (= neutron-proton ratio)Neutron excess (N-Z):32Isotopic mass:212.013001(11) u (atomic weight of Thorium-212)Nuclide mass:211.9636352 u (calculated nuclear mass without electrons)Mass excess:12.11035 MeVMass defect:1.748371632 u (per nucleus)Nuclear binding energy:1628.59768498 MeV (per nucleus)
7.68206455 MeV (average binding energy per nucleon)Separation energy:S_N = 9.87(7) MeV (first neutron)
S_P = 2.38(5) MeV (first proton)Half-life:31.7(13) msDecay constant λ:21.865841658042 s^-1Specific activity α:6.211282004047 × 10⁺²² Bq g^-1
1678724865958.8 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1980

Radioactive Decay

Half-life T_½ = 31.7(13) ms respectively 3.17 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁸Ra	ca. 99.7 %	7.958(5) MeV
EC/β⁺	²¹²Ac	ca. 0.3 %	4.83(5) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 122) and isobaric (same nucleon number A = 212) with Thorium-212. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 122	Isobar A = 212
74	¹⁹⁶W
75	¹⁹⁷Re
76	¹⁹⁸Os
77	¹⁹⁹Ir
78	²⁰⁰Pt
79	²⁰¹Au
80	²⁰²Hg	²¹²Hg
81	²⁰³Tl	²¹²Tl
82	²⁰⁴Pb	²¹²Pb
83	²⁰⁵Bi	²¹²Bi
84	²⁰⁶Po	²¹²Po
85	²⁰⁷At	²¹²At
86	²⁰⁸Rn	²¹²Rn
87	²⁰⁹Fr	²¹²Fr
88	²¹⁰Ra	²¹²Ra
89	²¹¹Ac	²¹²Ac
90	²¹²Th	²¹²Th
91	²¹³Pa	²¹²Pa
92	²¹⁴U