Thorium-207

Properties and data of the isotope ²⁰⁷Th.

Content

Thorium-207 is a radioisotope of the chemical element thorium which, in addition to the element-specific 90 protons, has 117 neutrons in the atomic nucleus, resulting in the mass number 207. The very short-lived, only artificially producible, unstable and therefore radioactive nuclide has no practical significance; dealing with ²⁰⁷Th is for academic purposes only.

The first report on the production of Th-207 dates back to 2022. The synthesis was successful at the Heavy Ion Research Facility in Lanzhou (HIRFL), a research facility in China, in a gas-filled recoil separator (SHANS) by the fusion reaction between argon-36 and hafnium-176 [1].

The nuclide decays with a half-life of about 9.7 milliseconds, releasing an alpha particle to radium-203.

General data

Name of the isotope:Thorium-207; Th-207Symbol:²⁰⁷Th or 20790ThMass number A:207 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:117Isotopic mass:207 u (atomic weight of Thorium-207)Nuclide mass:206.9506342 u (calculated nuclear mass without electrons)Mass excess:0 MeVMass defect:1.718048052 u (per nucleus)Nuclear binding energy:1600.35145215 MeV (per nucleus)
7.73116644 MeV (average binding energy per nucleon)Half-life:0.0097 sDecay constant λ:71.458472222675 s^-1Specific activity α:2.078903310921 × 10⁺²³ Bq g^-1
5618657597086.2 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:2022

Radioactive Decay

Half-life T_½ = 0.0097 s respectively 9.7 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰³Ra		8.167(21) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 117) and isobaric (same nucleon number A = 207) with Thorium-207. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 117	Isobar A = 207
71	¹⁸⁸Lu
72	¹⁸⁹Hf
73	¹⁹⁰Ta
74	¹⁹¹W
75	¹⁹²Re
76	¹⁹³Os
77	¹⁹⁴Ir
78	¹⁹⁵Pt	²⁰⁷Pt
79	¹⁹⁶Au	²⁰⁷Au
80	¹⁹⁷Hg	²⁰⁷Hg
81	¹⁹⁸Tl	²⁰⁷Tl
82	¹⁹⁹Pb	²⁰⁷Pb
83	²⁰⁰Bi	²⁰⁷Bi
84	²⁰¹Po	²⁰⁷Po
85	²⁰²At	²⁰⁷At
86	²⁰³Rn	²⁰⁷Rn
87	²⁰⁴Fr	²⁰⁷Fr
88	²⁰⁵Ra	²⁰⁷Ra
89	²⁰⁶Ac	²⁰⁷Ac
90	²⁰⁷Th	²⁰⁷Th