Thallium-202

Properties and data of the isotope ²⁰²Tl.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

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

General data

Name of the isotope:Thallium-202; Tl-202Symbol:²⁰²Tl or 20281TlMass number A:202 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:121Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.4938271604938 (= neutron-proton ratio)Neutron excess (N-Z):40Isotopic mass:201.9721091(17) u (atomic weight of Thallium-202)Nuclide mass:201.9276791 u (calculated nuclear mass without electrons)Mass excess:-25.98021 MeVMass defect:1.710173328 u (per nucleus)Nuclear binding energy:1593.01619399 MeV (per nucleus)
7.88621878 MeV (average binding energy per nucleon)Separation energy:S_N = 6.871(14) MeV (first neutron)
S_P = 5.6066(16) MeV (first proton)Half-life:12.31(8) dDecay constant λ:6.517089205553 × 10^-7 s^-1Specific activity α:1.952578566796 × 10⁺¹⁵ Bq g^-1
52772.393697211 Ci g^-1Spin and parity:
(nuclear angular momentum)2-Charge radius:5.4595(27) femtometer fmYear of discovery:1940

Radioactive Decay

Half-life T_½ = 12.31(8) d respectively 1.063584 × 10⁶ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	²⁰²Hg	100 %	1.3651(18) MeV

Parent Nuclides

Direct parent isotope is: ²⁰²Pb.

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
^202mTl	950.19(10) keV	591(3) μs	7+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 121) and isobaric (same nucleon number A = 202) with Thallium-202. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 121	Isobar A = 202
73	¹⁹⁴Ta
74	¹⁹⁵W
75	¹⁹⁶Re
76	¹⁹⁷Os	²⁰²Os
77	¹⁹⁸Ir	²⁰²Ir
78	¹⁹⁹Pt	²⁰²Pt
79	²⁰⁰Au	²⁰²Au
80	²⁰¹Hg	²⁰²Hg
81	²⁰²Tl	²⁰²Tl
82	²⁰³Pb	²⁰²Pb
83	²⁰⁴Bi	²⁰²Bi
84	²⁰⁵Po	²⁰²Po
85	²⁰⁶At	²⁰²At
86	²⁰⁷Rn	²⁰²Rn
87	²⁰⁸Fr	²⁰²Fr
88	²⁰⁹Ra	²⁰²Ra
89	²¹⁰Ac
90	²¹¹Th
91	²¹²Pa