Tantalum
. Tantalum, symbol Ta, white, ductile, malleable metallic element. Tantalum is one of the transition elements of the periodic table . The atomic number of tantalum is 73. Tantalum was first obtained in pure form in 1820 by the Swedish chemist Baron Jöns Jakob Berzelius , who heated potassium tantalifluoride, with excess potassium. PROPERTIES AND OCCURRENCE Tantalum is soluble in fused alkalies, insoluble in sulfuric, hydrochloric, and nitric acids, and soluble in hydrofluoric acid. It ignites in air to form tantalum pentoxide (sometimes referred to as tantalum(V) oxide or tantalic acid anhydride), a white infusible substance that combines with metallic oxides or hydroxides to form compounds called tantalites. Tantalic acid (also know as tantalum(V) oxide hydrate), is a gelatinous precipitate that has a varying number of water molecules associated with each tantalum pentoxide molecule. Tantalum melts at about 2996° C (about 5425° F), boils at about 5425° C (about 9797° F), and has a sp