Thallium-179

Properties and data of the isotope ¹⁷⁹Tl.

Contents

Thallium-179 is a radioisotope of the chemical element thallium, which has 98 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 179. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁷⁹Tl is exclusively for academic purposes.

According to a report from 1983, the radioactive nuclide ¹⁷⁹Tl was first produced and detected by irradiating a template of natural yttrium-89 with 4.5 - 5.4 MeV/u molybdenum-92 ions [1]:

⁸⁹Y(⁹²Mo,2n)¹⁷⁹Tl.

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

General data

Name of the isotope:Thallium-179; Tl-179Symbol:¹⁷⁹Tl or 17981TlMass number A:179 (= number of nucleons)Atomic number Z:81 (= number of protons)Neutrons N:98Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.2098765432099 (= neutron-proton ratio)Neutron excess (N-Z):17Isotopic mass:178.99112(4) u (atomic weight of Thallium-179)Nuclide mass:178.94669 u (calculated nuclear mass without electrons)Mass excess:-8.27167 MeVMass defect:1.49186936 u (per nucleus)Nuclear binding energy:1389.66735762 MeV (per nucleus)
7.76350479 MeV (average binding energy per nucleon)Separation energy:S_N = 11.728(109) MeV (first neutron)Half-life:0.437(9) sDecay constant λ:1.5861491545994 s^-1Specific activity α:5.366299794307 × 10⁺²¹ Bq g^-1
145035129575.88 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2+Year of discovery:1983

Radioactive Decay

Half-life T_½ = 0.437(9) s respectively 4.37 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy
α	¹⁷⁵Au	60 %	6.7091(26) MeV
EC/β⁺	¹⁷⁹Hg	40 %	8.663(48) MeV
p	¹⁷⁸Hg	?

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
^179mTl	825(10) keV	1.41(2) ms	(11/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 98) and isobaric (same nucleon number A = 179) with Thallium-179. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 98	Isobar A = 179
57	¹⁵⁵La
58	¹⁵⁶Ce
59	¹⁵⁷Pr
60	¹⁵⁸Nd
61	¹⁵⁹Pm
62	¹⁶⁰Sm
63	¹⁶¹Eu
64	¹⁶²Gd
65	¹⁶³Tb
66	¹⁶⁴Dy
67	¹⁶⁵Ho
68	¹⁶⁶Er
69	¹⁶⁷Tm	¹⁷⁹Tm
70	¹⁶⁸Yb	¹⁷⁹Yb
71	¹⁶⁹Lu	¹⁷⁹Lu
72	¹⁷⁰Hf	¹⁷⁹Hf
73	¹⁷¹Ta	¹⁷⁹Ta
74	¹⁷²W	¹⁷⁹W
75	¹⁷³Re	¹⁷⁹Re
76	¹⁷⁴Os	¹⁷⁹Os
77	¹⁷⁵Ir	¹⁷⁹Ir
78	¹⁷⁶Pt	¹⁷⁹Pt
79	¹⁷⁷Au	¹⁷⁹Au
80	¹⁷⁸Hg	¹⁷⁹Hg
81	¹⁷⁹Tl	¹⁷⁹Tl
82	¹⁸⁰Pb	¹⁷⁹Pb