Antimony
. Antimony, symbol Sb, bluish-white, brittle, semimetalic element. The atomic number of antimony is 51; the element is in group 15 (or Va) of the periodic table . Antimony's compounds were known in ancient times, and the element was probably discovered by the German alchemist Basil Valentine about 1450. It was certainly known by about 1600, but was confused with other elements, such as bismuth, tin, and lead. Antimony generally shows the properties of a metal, but sometimes shows those of a nonmetal. It exists in several distinctly different physical forms, the most common of which is metallic in appearance. Antimony ranks about 64th in natural abundance among the elements in crustal rock. The atomic weight of antimony is 121.75; it melts at about 630° C (about 1166° F), boils at about 1750° C (about 3182° F), and has a specific gravity of 6.7. It occasionally occurs as a free element, usually associated with silver, arsenic, or bismuth. It crystallizes in the hexagonal system (see...