Thorium-222

Properties and data of the isotope ²²²Th.

Content

General data

Name of the isotope:Thorium-222; Th-222Symbol:²²²Th or 22290ThMass number A:222 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:132Isotopic mass:222.018468(13) u (atomic weight of Thorium-222)Nuclide mass:221.9691022 u (calculated nuclear mass without electrons)Mass excess:17.20283 MeVMass defect:1.829553792 u (per nucleus)Nuclear binding energy:1704.21837993 MeV (per nucleus)
7.67665937 MeV (average binding energy per nucleon)Separation energy:S_N = 7.809(15) MeV (first neutron)
S_P = 4.61(5) MeV (first proton)Half-life:2.24(3) msDecay constant λ:309.44070560712 s^-1Specific activity α:8.394123950289 × 10⁺²³ Bq g^-1
22686821487269 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1970

Radioactive Decay

Half-life T_½ = 2.24(3) ms respectively 2.24 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹⁸Ra	100 %	8.127(5) MeV

Parent Nuclides

Direct parent isotope is: ²²⁶U.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 132) and isobaric (same nucleon number A = 222) with Thorium-222. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 132	Isobar A = 222
80	²¹²Hg
81	²¹³Tl
82	²¹⁴Pb
83	²¹⁵Bi	²²²Bi
84	²¹⁶Po	²²²Po
85	²¹⁷At	²²²At
86	²¹⁸Rn	²²²Rn
87	²¹⁹Fr	²²²Fr
88	²²⁰Ra	²²²Ra
89	²²¹Ac	²²²Ac
90	²²²Th	²²²Th
91	²²³Pa	²²²Pa
92	²²⁴U	²²²U
93	²²⁵Np