Tellurium
. Tellurium (Latin tellus,”earth”), symbol Te, silver-white, brittle, semimetallic element. The atomic number of tellurium is 52. Tellurium was first discovered in 1782 by the German scientist Franz Joseph Müller von Reichenstein; it was recognized as an element and given its name in 1798 by the German chemist Martin Heinrich Klaproth . PROPERTIES AND OCCURRENCE Tellurium is a comparatively stable element, insoluble in water and hydrochloric acid but soluble in nitric acid and aqua regia . Tellurium reacts with an excess of chlorine to form tellurium dichloride, and tellurium tetrachloride. It is oxidized by nitric acid to produce tellurium dioxide, and by chromic acid to produce telluric acid. In combination with hydrogen or certain metals, it forms tellurides such as hydrogen telluride and sodium telluride. Tellurium melts at about 452° C (about 846° F), boils at about 1390° C (about 2534° F), and has a specific gravity of 6.25. The atomic weight of tellurium is 127.60. Tellurium ra