Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, ductile and silvery- White metal that tarnishes when exposed to air, and it is soft enough to be cut with a knife. It is the second element in the lanthanide series, and while it often shows the +3 oxidation state characteristic of the series, it also exceptionally has a stable +4 state that does not oxidize water. It is also considered one of the rare-earth elements.
It was discovered, in Bastnäs, Sweden, by Jons Jakob Berzelius and Wilhelm Hisinger in 1803, and independently by Martin Heinrich Klaproth in Germany in the same year. In 1839 Carl Gustaf Mosander became the first to isolate the metal. Today, cerium and its compounds have a variety of uses: for example, cerium(IV) oxide is used to polish glass and is an important part of catalytic converters. Cerium metal is used in ferrocerium lighters for its pyrophoric properties. Cerium-doped YAG phosphor is used in conjunction with blue light-emitting diodes to produce white light in most commercial white LED light sources.
Physical Properties of Cerium
- It reacts readily in the air and tarnishes gradually. It oxidizes rapidly in hot water, slowly in cold water and dissolves in the acids.
- It is one of the most abundant among the rare earth elements.
- It is found in lanthanides and makes about 0.0046% of Earth’s crust weight.
- The production of cerium marks up to 23000 tonnes per a year which may increase as more cerium is used nowadays.
- Cerium has no biological role. and not toxic.
- It has a variable electronic structure. The energy of the 4f electron is nearly the same as that of the outer 5d and 6s electrons that are delocalized in the metallic state, and only a small amount of energy is required to change the relative occupancy of these electronic levels. This gives rise to dual valence states.