Thorium-215

Properties and data of the isotope ²¹⁵Th.

Content

General data

Name of the isotope:Thorium-215; Th-215Symbol:²¹⁵Th or 21590ThMass number A:215 (= number of nucleons)Atomic number Z:90 (= number of protons)Neutrons N:125Isotopic mass:215.011725(9) u (atomic weight of Thorium-215)Nuclide mass:214.9623592 u (calculated nuclear mass without electrons)Mass excess:10.92177 MeVMass defect:1.77564238 u (per nucleus)Nuclear binding energy:1654.00022312 MeV (per nucleus)
7.69302429 MeV (average binding energy per nucleon)Separation energy:S_N = 7.845(14) MeV (first neutron)
S_P = 2.811(18) MeV (first proton)Half-life:1.2(2) sDecay constant λ:0.57762265046662 s^-1Specific activity α:1.617918588372 × 10⁺²¹ Bq g^-1
43727529415.462 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2-)Year of discovery:1968

Radioactive Decay

Half-life T_½ = 1.2(2) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹¹Ra	100 %	7.665(4) MeV

Parent Nuclides

Direct parent isotope is: ²¹⁹U.

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^215mTh	1421.3+x keV	0.77(6) μs

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 125) and isobaric (same nucleon number A = 215) with Thorium-215. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 125	Isobar A = 215
76	²⁰¹Os
77	²⁰²Ir
78	²⁰³Pt
79	²⁰⁴Au
80	²⁰⁵Hg	²¹⁵Hg
81	²⁰⁶Tl	²¹⁵Tl
82	²⁰⁷Pb	²¹⁵Pb
83	²⁰⁸Bi	²¹⁵Bi
84	²⁰⁹Po	²¹⁵Po
85	²¹⁰At	²¹⁵At
86	²¹¹Rn	²¹⁵Rn
87	²¹²Fr	²¹⁵Fr
88	²¹³Ra	²¹⁵Ra
89	²¹⁴Ac	²¹⁵Ac
90	²¹⁵Th	²¹⁵Th
91	²¹⁶Pa	²¹⁵Pa
92	²¹⁷U	²¹⁵U