Tl-208

Thallium-208 (Tl-208) is a radioactive isotope of thallium with a half-life of approximately 3.05 minutes. It is part of the thorium-232 decay series and is produced as a result of the radioactive decay of its parent isotopes, such as radium-224 and thorium-228. Tl-208 undergoes beta decay, emitting high-energy beta particles and gamma radiation, with prominent gamma-ray energies at 2614.5 keV, making it highly detectable through gamma spectrometry.

Tl-208 does not occur independently in nature but is found as part of the thorium decay series, primarily in thorium-containing minerals such as monazite and thorite. It is present in trace amounts wherever thorium-232 is found and contributes to natural background radiation.

It is always present in thorium-232 and is not found separately from thorium.

Thorium is a very common isotope, both in nature and in the home. It is used to make special alloys for electrodes, gas lamp nets, and is found in minerals, building materials (often granite), etc.