Diane Gaylord, age 13, of Baron Rouge, La., for her questions:

WHERE DO WE GET TANTALUM?

Tantalum is a chemical element that is used to make tantalum pentoxide, a thin layer of which is used to protect the metal surface of industrial chemical apparatus, surgical instruments and aircraft and missile parts.

Tantalum is not found as a metal. It occurs chiefly in the mineral tantalite and is separated from an element called niobium and converted into a metal by chemical processes.

Tantalum resists attack by almost all chemicals at ordinary temperatures. For this reason it is used to make corrosion resistant items. Mixtures of tantalum and other metals make strong, useful alloys.

Tantalum combines with oxygen to form tantalum pentoxide. This compound is widely used to make capacitors or electronic devices for storing electricity. The compound is an important ingredient in camera lenses because it increases the refracting or light bending power of glass.

Tantalum was discovered in 1802 by a Swedish scientist named Anders Akeberg.