Tantalum - Ta, 73

Tantalum is a heavy, hard gray metal. Pure tantalum is ductile and may be drawn into very fine wire. Tantalum is practically immune to chemical attack at temperatures lower than 150 °C. It is only attacked by hydrofluoric acid, acidic solutions of the fluoride ion, and free sulfur trioxide. Alkalis attack tantalum very slowly. At higher temperatures, tantalum is more reactive. The melting point of tantalum is very high, exceeded only by that of tungsten and rhenium. The melting point of tantalum is 2996 °C; boiling point is 5425 +/- 100 °C; specific gravity is 16.654; valence is usually 5, but may be 2, 3, or 4.

Tantalum wire is used as a filament for evaporating other metals. Tantalum is incorporated into a variety of alloys, conferring high melting point, ductility, strength, and corrosion resistance. Tantalum carbide is one of the hardest materials ever made. At high temperatures, tantalum has good 'gettering' ability. Tantalum oxide films are stable, with desirable dielectric and rectifying properties. The metal is used in chemical process equipment, vacuum furnaces, capacitors, nuclear reactors, and aircraft parts. Tantalum oxide may be used to make a glass with a high index of refraction, with applications including use for camera lenses. Tantalum is immune to body liquids and is a non-irritating metal. Therefore, it has widespread surgical applications.