Thallium is a chemical element wi seembol Tl an atomic nummer 81. This saft gray poor metal is nae foond free in naitur. When isolated, it resembles tin, but discolors when exposed tae air. Chemists William Crookes an Claude-Auguste Lamy discovered thallium independently in 1861, in residues o sulfuric acid production. Baith uised the newly developit method o flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, frae Greekθαλλός, thallos, meanin "a green shuit or twig," wis named bi Crookes. It wis isolatit bi electrolysis a year later, bi Lamy.
