205Tl

205Tl is a stable isotope of the element thallium (atomic number 81) with mass number 205. It is one of two long-lived, naturally occurring thallium isotopes, the other being 203Tl. In natural thallium, 205Tl is the more abundant isotope, accounting for roughly two-thirds to three-quarters of the element, with 203Tl comprising the remaining portion.

Natural occurrence and production: 205Tl, like other thallium isotopes, occurs only in trace amounts in minerals. Thallium itself is typically obtained as a byproduct of refining zinc, copper, and lead ores. The two stable thallium isotopes together constitute essentially all natural thallium, and isotopic separation is not generally required for commercial use.

Nuclear properties: 205Tl is considered a stable nuclide and does not undergo radioactive decay under normal conditions. Its stability means it does not contribute to radiological hazards through decay in the way that many other isotopes do, though thallium compounds as a class are highly toxic.

Applications: Because of its stability, 205Tl has limited specialized applications. It is used in isotopic analysis and mass spectrometry as a reference or tracer in certain analytical procedures and contributes to studies of thallium isotopic composition in geology and environmental samples.

Safety: Thallium and its compounds are highly toxic and can be absorbed through skin or inhalation. Handling requires appropriate laboratory controls and waste disposal procedures to prevent exposure.

See also: Isotopes of thallium, Thallium.