Thallium-205

Properties and data of the isotope ²⁰⁵Tl.

Contents

General Data

Parent Nuclides

NMR Data

Isotones und Isobares

Literature

Thallium-205 is a stable isotope of the chemical element thallium, which has 124 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 205.

The first observation and identification of the nuclide ²⁰⁵Tl using a Cavendish mass spectrometer was reported in 1931 [1].

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

General data

Name of the isotope:Thallium-205; Tl-205Symbol:²⁰⁵Tl or 20581TlMass number A:205 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:124Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.5308641975309 (= neutron-proton ratio)Neutron excess (N-Z):43Isotopic mass:204.974428(9) u (atomic weight of Thallium-205)Nuclide mass:204.929998 u (calculated nuclear mass without electrons)Mass excess:-23.82016 MeVMass defect:1.733849176 u (per nucleus)Nuclear binding energy:1615.07010435 MeV (per nucleus)
7.87839075 MeV (average binding energy per nucleon)Separation energy:S_N = 7.5461(5) MeV (first neutron)
S_P = 6.4196(13) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)1/2+Magnetic dipole moment:μ(μ_N) = + 1.6382146Charge radius:5.4759(26) femtometer fmYear of discovery:1931

Parent Nuclides

Direct parent isotopes are: ²⁰⁵Pb, ²⁰⁵Hg, ²⁰⁹Bi.

Occurrence

Comparison of the natural Thallium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Thallium Isotopic mixture	204.38 u	100 %
Isotope ²⁰⁵Tl	204.974428(9) u	70.48(1) % [70.41 - 70.56 %]	stable	1/2+
Isotope ²⁰³Tl	202.972345(9) u	29.52(1) % [29.44 - 29.59 %]	stable	1/2+

NMR data

Nuclear magnetic properties and parameters of the NMR active Nuclide ²⁰⁵Tl

Isotope:²⁰⁵Tl-NMRQuantity:70.48(1) % [70.41 - 70.56 %]Spin:1/2+Nuclearmagnetic moment
μ/μ_N:+ 1.6382146Gyromagnetic ratio γ:15.6922 · 10⁷ rad T^-1 s^-1
24.97491 MHz T^-1Nuclear g-factor:g_l = 3.2764292Resonance frequency:v₀ = 24.9749 MHz at 1 TRelative Sensitivity:[related to ¹H = 1.000]:
0.20182 (H₀ = const.)
0.5866 (v₀ = const.)
0.142 (at natural abundance)
relative receptivity as compared to ¹³C:
836 (at natural abundance)Reference compound:
(conditions)A very dilute solution of thallium(I) nitrate in water (The highly hydrolysis-sensitive thallium(III) nitrate is incorrectly listed in some publications).Frequency ratio:Ξ(²⁰⁵Tl) = 57.68383 % [based on the reference substance]

²⁰⁵Tl is the more sensitive and less broad line-producing atomic nucleus of the two natural NMR-active isotopes thallium-203 and Thallium-205, which is why it is more frequently used for Tl-NMR spectroscopy.

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
^205m1Tl	3290.61(17) keV	2.6(2) μs	25/2+
^205m2Tl	4835.6(15) keV	235(10) ns	(35/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 124) and isobaric (same nucleon number A = 205) with Thallium-205. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 124	Isobar A = 205
75	¹⁹⁹Re
76	²⁰⁰Os
77	²⁰¹Ir	²⁰⁵Ir
78	²⁰²Pt	²⁰⁵Pt
79	²⁰³Au	²⁰⁵Au
80	²⁰⁴Hg	²⁰⁵Hg
81	²⁰⁵Tl	²⁰⁵Tl
82	²⁰⁶Pb	²⁰⁵Pb
83	²⁰⁷Bi	²⁰⁵Bi
84	²⁰⁸Po	²⁰⁵Po
85	²⁰⁹At	²⁰⁵At
86	²¹⁰Rn	²⁰⁵Rn
87	²¹¹Fr	²⁰⁵Fr
88	²¹²Ra	²⁰⁵Ra
89	²¹³Ac	²⁰⁵Ac
90	²¹⁴Th
91	²¹⁵Pa
92	²¹⁶U