👉 Thallium is a chemical element with symbol Th and atomic number 46. It is one of the lightest elements in the periodic table, with a density of approximately 5.02 g/cm³ at standard temperature and pressure (STP). Thallium has several unique properties that make it useful for various applications. Thallium is used in a variety of industries, including electronics, medicine, energy, and materials science. It is the active ingredient in the radioisotope
