Thallium-179m
Properties and data of the isotope 179mTl.
See also: List of individual Thallium isotopes (and general data sources).
General data
Name of the isotope:Thallium-179m; Tl-179mSymbol:179mTl or 179m81TlMass 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):17Excitation energy:825(10) keVIsotopic mass:178.99112(4) u (atomic weight of Thallium-179m)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)Half-life:1.41(2) msDecay constant λ:491.59374507798 s-1Specific activity α:1.663172347597 × 10+24 Bq g-1
44950603989119 Ci g-1Spin and parity:
(nuclear angular momentum)(11/2-)Year of discovery:1983
Radioactive Decay
Half-life T½ = 1.41(2) ms respectively 1.41 × 10-3 seconds s.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| α | 175Au | 100 % | | |
| Iso | 179Tl | ? | | |
| EC/β+ | 180Hg | ? | | |
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 |
|---|
| 179Tl | | 0.437(9) s | 1/2+ |
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-179m. 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 |
Literature and References
[1] - A. N. Andreyev et al.:
The new isotope 179Pb and α-decay properties of 179Tlm.
In: Journal of Physics G: Nuclear and Particle Physics, 37, 035102, (2010), DOI 10.1088/0954-3899/37/3/035102.
Last update: 2025-12-20
Perma link: https://www.chemlin.org/isotope/thallium-179m
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