The Lanthanoid Series
Members of the Lanthanoid Series
The fifteen members of this series are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.
Properties
The lanthanoids are not as rare as was once thought; even the scarce rare earths (e.g., europium, lutetium) are more common than the platinum-group metals. Several of the lanthanoids form during the fission of uranium and plutonium.
All lanthanoids closely resemble lanthanum. They are shiny and silvery-white, and tarnish easily when exposed to air. Many are used to make steel. They react violently with most nonmetals. They are relatively soft but their hardness increases with their atomic number. lanthanoids burn in air.
They have high melting and boiling points.
Many rare earth compounds fluoresce strongly under ultraviolet light.
Reactions
All lanthanoids are very reactive.
React with water to liberate hydrogen gas (H2), slowly in cold/quickly upon heating. Lanthanoids commonly bind to water.
React with H+ (dilute acid) to release H2 (rapidly at room temperature).
React in an exothermic reaction with H2.
Burn easily in air.
At elevated temperatures, many rare earths ignite and burn vigorously.
The lanthanoids react readily with most nonmetals and form binaries on heating with most nonmetals.
Uses
They have many scientific and industrial uses. Their compounds are used as catalysts in the production of petroleum and synthetic products. lanthanoids are used in lamps, lasers, magnets, phosphors, motion picture projectors, and X-ray intensifying screens. A pyrophoric mixed rare-earth alloy called Mischmetall (50% Ce, 25% La, 25% other light lanthanoids) or misch metal is combined with iron to make flints for cigarette lighters. The addition of less than 1% Mischmetall or lanthanoids silicides improves the strength and workability of low alloy steels.
Most lanthanoids are widely used in lasers. These elements deflect UV and Infrared electromagnetic radiation and are commonly used in the production of sunglass lenses.