cerium

Cerium is a chemical element with the symbol Ce and atomic number 58. It is a member of the lanthanide series and is the most abundant of the rare earth elements in the Earth's crust, occurring primarily in minerals such as monazite and bastnäsite. The element was named after the asteroid Ceres, discovered two years earlier.

Physically, cerium is a soft, silvery metal that readily tarnishes in air. It forms oxides and intermetallics and is generally reactive, especially at elevated temperatures. In chemistry, it commonly exhibits the +3 and +4 oxidation states. Ce4+ compounds, especially cerium(IV) oxide (CeO2), are strong oxidants in acidic solutions and play a central role in many catalytic and polishing applications.

Occurrence and production revolve around its separation from other rare earth elements. Cerium is typically extracted from minerals such as monazite and bastnäsite, then refined through series of solvent extractions and reductions to produce cerium oxide or metal. The most common commercial form is cerium oxide (ceria), used in various industrial processes.

Isotopes: natural cerium consists of several isotopes, with Ce-136, Ce-138, Ce-140, and Ce-142 being the principal stable ones. Some radioisotopes occur in trace amounts or are produced in nuclear reactions, but natural cerium is predominantly non-radioactive.

Applications are diverse. Cerium oxide is widely used as a polishing powder for glass and lenses and as a catalyst in automotive catalytic converters. It also serves in various catalysts, glass and ceramic pigments, ultraviolet shielding, and oxygen sensors. In metallurgy, cerium is used as a deoxidizer and alloying element.

Historically, cerium was identified in the early 19th century and named for Ceres. It has since become important in materials science, catalysis, and industrial chemistry due to its redox flexibility and oxide chemistry.