Isotopes of thallium

Thallium has two stable isotopes and one of these, Tl-203, is used to produce one of the (workhorses( of nuclear medicine: Tl-201. Tl-201 is used extensively for imaging and in particular for perfusion tests of the myocardium. These tests are done to determine the damage to the heart from a heart attack or from heart diseases. Tl205 has been proposed as an alternative target for the production of Tl-201. Tl-205 is also used in nuclear magnetic resonance research. Thallium isotopes can be obtained from Trace Sciences International.

Naturally occurring isotopes

This table shows information about naturally occuring isotopes, their atomic masses, their natural abundances, their nuclear spins, and their magnetic moments. Further data for radioisotopes (radioactive isotopes) of thallium are listed (including any which occur naturally) below.
Isotope Atomic mass (ma/u) Natural abundance (atom %) Nuclear spin (I) Magnetic moment (μ/μN)
203Tl 202.972320 (5) 29.524 (14) 1/2 1.622257
205Tl 204.974401 (5) 70.476 (14) 1/2 1.6382135

Isotopic abundances of Tl
In the above picture, the most intense ion is set to 100% since this corresponds best to the output from a mass spectrometer. This is not to be confused with the relative percentage isotope abundances which total 100% for all the naturally occurring isotopes.

Radiosotope data

Further data for naturally occuring isotopes of thallium are listed above. This table gives information about some radiosotopes of thallium, their masses, their half-lives, their modes of decay, their nuclear spins, and their nuclear magnetic moments.
Isotope Mass Half-life Mode of decay Nuclear spin Nuclear magnetic moment
200Tl 199.97095 1.087 d EC to 200Hg 2 0.04
201Tl 200.97078 3.040 d EC to 201Hg 1/2 1.605
202Tl 201.97209 12.23 d EC to 202Hg 2 0.06
204Tl 203.97385 3.78 y EC to 204Hg; β- to 204Pb 2 0.09

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  1. Naturally occurring isotope abundances: Commission on Atomic Weights and Isotopic Abundances report for the International Union of Pure and Applied Chemistry in Isotopic Compositions of the Elements 1989, Pure and Applied Chemistry, 1998, 70, 217. [Copyright 1998 IUPAC]
  2. For further information about radioisotopes see Jonghwa Chang's (Korea Atomic Energy Research Institute) Table of the Nuclides
  3. Masses, nuclear spins, and magnetic moments: I. Mills, T. Cvitas, K. Homann, N. Kallay, and K. Kuchitsu in Quantities, Units and Symbols in Physical Chemistry, Blackwell Scientific Publications, Oxford, UK, 1988. [Copyright 1988 IUPAC]

NMR Properties of thallium

Common reference compound: TlNO3/D2O.

Table of NMR-active nucleus propeties of thallium
  Isotope 1 Isotope 2 Isotope 3
Isotope 203Tl 205Tl
Natural abundance /% 29.524 70.476
Spin (I) 1/2 1/2
Frequency relative to 1H = 100 (MHz) 57.123200 57.633833
Receptivity, DP, relative to 1H = 1.00 0.0578 0.142
Receptivity, DC, relative to 13C = 1.00 331 813
Magnetogyric ratio, γ (107 rad T-1 s-1) 15.5393338 15.6921808
Magnetic moment, μ (μN) 2.80983305 2.83747094
Nuclear quadrupole moment, Q/millibarn - -
Line width factor, 1056l (m4) - -


  1. R.K. Harris in Encyclopedia of Nuclear Magnetic Resonance, D.M. Granty and R.K. Harris, (eds.), vol. 5, John Wiley & Sons, Chichester, UK, 1996. I am grateful to Professor Robin Harris (University of Durham, UK) who provided much of the NMR data, which are copyright 1996 IUPAC, adapted from his contribution contained within this reference.
  2. J. Mason in Multinuclear NMR, Plenum Press, New York, USA, 1987. Where given, data for certain radioactive nuclei are from this reference.
  3. P. Pyykkö, Mol. Phys., 2008, 106, 1965-1974.
  4. P. Pyykkö, Mol. Phys., 2001, 99, 1617-1629.
  5. P. Pyykkö, Z. Naturforsch., 1992, 47a, 189. I am grateful to Professor Pekka Pyykkö (University of Helsinki, Finland) who provided the nuclear quadrupole moment data in this and the following two references.
  6. D.R. Lide, (ed.), CRC Handbook of Chemistry and Physics 1999-2000 : A Ready-Reference Book of Chemical and Physical Data (CRC Handbook of Chemistry and Physics, CRC Press, Boca Raton, Florida, USA, 79th edition, 1998.
  7. P. Pyykkö, personal communication, 1998, 204, 2008, 2010.
  8. The isotopic abundances are extracted from the naturally occurring isotopes section within WebElements.

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thallium atomic number