Thorium-218

Properties and data of the isotope ²¹⁸Th.

Content

General data

Name of the isotope:Thorium-218; Th-218Symbol:²¹⁸Th or 21890ThMass number A:218 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:128Isotopic mass:218.013276(11) u (atomic weight of Thorium-218)Nuclide mass:217.9639102 u (calculated nuclear mass without electrons)Mass excess:12.36651 MeVMass defect:1.800086128 u (per nucleus)Nuclear binding energy:1676.76942772 MeV (per nucleus)
7.69160288 MeV (average binding energy per nucleon)Separation energy:S_N = 7.910(15) MeV (first neutron)
S_P = 3.626(15) MeV (first proton)Half-life:117(9) nsDecay constant λ:5924334.8765807 s^-1Specific activity α:1.636567849917 × 10⁺²⁸ Bq g^-1
4.423156351128 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1973

Radioactive Decay

Half-life T_½ = 117(9) ns respectively 1.17 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹⁴Ra	100 %	9.849(9) MeV

Parent Nuclides

Direct parent isotope is: ²²²U.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 128) and isobaric (same nucleon number A = 218) with Thorium-218. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 128	Isobar A = 218
77	²⁰⁵Ir
78	²⁰⁶Pt
79	²⁰⁷Au
80	²⁰⁸Hg
81	²⁰⁹Tl
82	²¹⁰Pb	²¹⁸Pb
83	²¹¹Bi	²¹⁸Bi
84	²¹²Po	²¹⁸Po
85	²¹³At	²¹⁸At
86	²¹⁴Rn	²¹⁸Rn
87	²¹⁵Fr	²¹⁸Fr
88	²¹⁶Ra	²¹⁸Ra
89	²¹⁷Ac	²¹⁸Ac
90	²¹⁸Th	²¹⁸Th
91	²¹⁹Pa	²¹⁸Pa
92	²²⁰U	²¹⁸U
95	²²³Am