Thallium-199

Properties and data of the isotope ¹⁹⁹Tl.

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-199; Tl-199Symbol:¹⁹⁹Tl or 19981TlMass number A:199 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:118Isotopic mass:198.96988(3) u (atomic weight of Thallium-199)Nuclide mass:198.92545 u (calculated nuclear mass without electrons)Mass excess:-28.0566 MeVMass defect:1.68640768 u (per nucleus)Nuclear binding energy:1570.87863547 MeV (per nucleus)
7.89386249 MeV (average binding energy per nucleon)Separation energy:S_N = 8.602(29) MeV (first neutron)
S_P = 4.394(28) MeV (first proton)Half-life:7.42(8) hDecay constant λ:2.594890613057 × 10^-5 s^-1Specific activity α:7.89232161008 × 10⁺¹⁶ Bq g^-1
2133059.8946165 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2+Magnetic dipole moment:μ(μ_N) = + 160(2)Nuclear g-factor:g_l = 320Charge radius:5.4479(31) femtometer fmYear of discovery:1949

Radioactive Decay

Half-life T_½ = 7.42(8) h (hours) respectively 2.6712 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹⁹⁹Hg	100 %	1.487(28) MeV

Parent Nuclides

Direct parent isotope is: ¹⁹⁹Pb.

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
^199mTl	748.87(6) keV	28.4(2) ms	9/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 118) and isobaric (same nucleon number A = 199) with Thallium-199. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 118	Isobar A = 199
72	¹⁹⁰Hf
73	¹⁹¹Ta
74	¹⁹²W
75	¹⁹³Re	¹⁹⁹Re
76	¹⁹⁴Os	¹⁹⁹Os
77	¹⁹⁵Ir	¹⁹⁹Ir
78	¹⁹⁶Pt	¹⁹⁹Pt
79	¹⁹⁷Au	¹⁹⁹Au
80	¹⁹⁸Hg	¹⁹⁹Hg
81	¹⁹⁹Tl	¹⁹⁹Tl
82	²⁰⁰Pb	¹⁹⁹Pb
83	²⁰¹Bi	¹⁹⁹Bi
84	²⁰²Po	¹⁹⁹Po
85	²⁰³At	¹⁹⁹At
86	²⁰⁴Rn	¹⁹⁹Rn
87	²⁰⁵Fr	¹⁹⁹Fr
88	²⁰⁶Ra
89	²⁰⁷Ac
90	²⁰⁸Th