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Isotopes of thallium

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Isotopes of thallium
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Thallium (81Tl) has 42 isotopes with atomic masses that range from 176 to 217. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years. 207Tl, with a half-life of 4.77 minutes, has the longest of naturally occurring Tl radioisotopes. All isotopes of thallium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

Quick Facts Main isotopes, Decay ...

Thallium-202 (half-life 12.31 days) can be made in a cyclotron[4] while thallium-204 (half-life 3.78 years) is made by the neutron activation of stable thallium in a nuclear reactor.[5]

In the fully ionized state, the isotope 205Tl81+ becomes unstable, undergoing bound-state β− decay to 205Pb81+ with a half-life of 291+33
−27 days,[6][7] but 203Tl remains stable.

205Tl is the decay product of bismuth-209, an isotope that was once thought to be stable but is now known to undergo alpha decay with an extremely long half-life of 2.01×1019 y.[8] Thus 205Tl is now placed at the end of the neptunium decay chain.

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The neptunium decay chain, ending at 205Tl.
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List of isotopes

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More information Nuclide, Historic name ...
  1. [n 1]
    mTl – Excited nuclear isomer.
  2. [n 2]
    ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. [n 3]
    # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. [n 4]
    # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. [n 5]
    Modes of decay:
    α:Alpha decay
    β+:Positron emission
    EC:Electron capture
    β−:Beta decay
    IT:Isomeric transition
    SF:Spontaneous fission
    n:Neutron emission
    p:Proton emission
  6. [n 6]
    Bold symbol as daughter – Daughter product is stable.
  7. [n 7]
    ( ) spin value – Indicates spin with weak assignment arguments.
  8. [n 8]
    Order of ground state and isomer is uncertain.
  9. [n 9]
    Main isotope used in scintigraphy
  10. [N 10]
    Believed to undergo α decay to 199Au
  11. [N 11]
    Final decay product of 4n+1 decay chain (the Neptunium series)
  12. [N 12]
    Believed to undergo α decay to 201Au
  13. [N 13]
    Can undergo bound-state β− decay to 205Pb81+ with a half-life of 291+33
    −27     days when fully ionized[7]
  14. [N 14]
    Intermediate decay product of 238U
  15. [N 15]
    Intermediate decay product of 235U
  16. [N 16]
    Intermediate decay product of 232Th
  17. [N 17]
    Intermediate decay product of 237Np
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Thallium-201

Thallium-201 (201Tl) is a synthetic radioisotope of thallium. It has a half-life of 73 hours and decays by electron capture, emitting X-rays (~70–80 keV), and photons of 135 and 167 keV in 10% total abundance.[11] Thallium-201 is synthesized by the neutron activation of stable thallium in a nuclear reactor,[11][12] or by the 203Tl(p, 3n)201Pb nuclear reaction in cyclotrons, as 201Pb naturally decays to 201Tl afterwards.[13] It is a radiopharmaceutical, as it has fair imaging characteristics without excessive patient radiation dose. It was the most popular isotope used for nuclear cardiac stress tests.[14] Thallium 201 has largely been replaced by Technetium 99m, which has a shorter half-life (6 hours vs 73 hours) and a single high energy peak (140 keV), which is better for imaging than the 3 energy peaks with thallium 201. Thallium 201 is mostly used for myocardial viability studies. It will redistribute in body tissues, whereas Tc99m will not. Tl 201 is taken up by the cardiac muscle via Na+/K+ pumps. Delayed imaging will show uptake in damaged, but still living myocardial cells, that would otherwise appear as a scar with Tc or Rb 82.

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See also

Daughter products other than thallium

References

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