Thallium-204

Properties and data of the isotope ²⁰⁴Tl.

Contents

Thallium-204 is a radioisotope of the chemical element thallium, which has 123 neutrons in its atomic nucleus in addition to the element-specific 81 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 204.

The discovery of the nuclide ²⁰⁴Tl by irradiation of thallous nitrate (isotopic composition see there) with neutrons was reported in 1953 [1].

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

General data

Name of the isotope:Thallium-204; Tl-204Symbol:²⁰⁴Tl or 20481TlMass number A:204 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:123Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.5185185185185 (= neutron-proton ratio)Neutron excess (N-Z):42Isotopic mass:203.9738634(12) u (atomic weight of Thallium-204)Nuclide mass:203.9294334 u (calculated nuclear mass without electrons)Mass excess:-24.34609 MeVMass defect:1.72574886 u (per nucleus)Nuclear binding energy:1607.5247086 MeV (per nucleus)
7.88002308 MeV (average binding energy per nucleon)Separation energy:S_N = 6.65608(29) MeV (first neutron)
S_P = 6.3658(13) MeV (first proton)Half-life:3.783(12) aDecay constant λ:5.806232582414 × 10^-9 s^-1Specific activity α:17224606146233 Bq g^-1
465.52989584414 Ci g^-1Spin and parity:
(nuclear angular momentum)2-Magnetic dipole moment:μ(μ_N) = 0.09(1)Nuclear g-factor:g_l = 0.045Charge radius:5.4704(28) femtometer fmYear of discovery:1953

Radioactive Decay

Half-life T_½ = 3.783(12) a respectively 1.19379851 × 10⁸ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	²⁰⁴Hg	2.92(7) %	0.3441(13) MeV
β^-	²⁰⁴Pb	97.08(7) %	0.76375(18) MeV

Radioactive decay chain of the isotope thallium-204

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
^204m1Tl	1103.9(3) keV	61.7(10) μs	(7)+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 123) and isobaric (same nucleon number A = 204) with Thallium-204. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 123	Isobar A = 204
74	¹⁹⁷W
75	¹⁹⁸Re
76	¹⁹⁹Os
77	²⁰⁰Ir	²⁰⁴Ir
78	²⁰¹Pt	²⁰⁴Pt
79	²⁰²Au	²⁰⁴Au
80	²⁰³Hg	²⁰⁴Hg
81	²⁰⁴Tl	²⁰⁴Tl
82	²⁰⁵Pb	²⁰⁴Pb
83	²⁰⁶Bi	²⁰⁴Bi
84	²⁰⁷Po	²⁰⁴Po
85	²⁰⁸At	²⁰⁴At
86	²⁰⁹Rn	²⁰⁴Rn
87	²¹⁰Fr	²⁰⁴Fr
88	²¹¹Ra	²⁰⁴Ra
89	²¹²Ac	²⁰⁴Ac
90	²¹³Th
91	²¹⁴Pa
92	²¹⁵U