Lanthanum

Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft metal with a silvery color that reacts rapidly with air and water. It belongs to the group of rare earth metals and is considered the first element of the series known as the lanthanides — a series that takes its name from lanthanum itself.

The name comes from the Greek word lanthanein, meaning 'to hide'. Lanthanum chemistry occurs predominantly at oxidation state +3, making it uniform in its reactions with oxygen, halogens, and acids. Its melting point is approximately 920 degrees Celsius, and its density is about 6.1 grams per cubic centimeter.

History of Discovery

Lanthanum was isolated in 1839 by Swedish chemist Carl Gustav Mosander, who obtained it from a substance he had previously thought to be pure cerium. It was not until much later that pure metallic lanthanum could be produced, because the separation of rare earth metals from one another is difficult and requires many chemical steps.

Sources

Lanthanum does not occur freely in nature; it is extracted from ores including monazite and bastnäsite, which contain other rare earth elements as well. The extraction process involves chemical separation (solvent extraction) followed by metal reduction. Although called 'rare earth' metals, lanthanum is not particularly scarce in the Earth's crust; the difficulty lies in separation rather than in abundance.

Uses

The primary use is in metal alloys for nickel-metal hydride (NiMH) batteries, which power cordless devices and portable equipment. It is also used in camera lenses and telescopes, since lanthanum oxide increases the refractive index of light. In petroleum refining, lanthanum alloys are incorporated into catalysts for fluid catalytic cracking (FCC). In medicine, lanthanum carbonate is used to reduce phosphate levels in patients with kidney disease.