Cerium is a silvery metal, belonging to the lanthanide group. It resembles iron in color and luster, but is soft, and both malleable and ductile. Cerium has the longest liquid range of any non-radioactive element: 2648 °C (795 °C to 3443 °C) or 4766 °F (1463 °F to 6229 °F). (Thorium has a longer liquid range.)
Although cerium belongs to chemical elements group called rare earth metals, it is in fact more common than lead. Cerium is available in relatively large quantities (68 ppm in Earth’s crust). It is used in some rare-earth alloys.
Among rare earth elements only europium is more reactive. It tarnishes readily in the air. Alkali solutions and dilute and concentrated acids attack the metal rapidly. Cerium oxidizes slowly in cold water and rapidly in hot water. The pure metal can ignite if scratched.
Cerium(IV) (ceric) salts are orange red or yellowish, whereas cerium(III) (cerous) salts are usually white or colorless. Both oxidation states absorb ultraviolet light strongly. Cerium(III) can be used to make glasses that are colorless, yet absorb ultraviolet light almost completely. Cerium can be readily detected in rare earth mixtures by a very sensitive qualitative test: addition of ammonia and hydrogen peroxide to an aqueous solution of lanthanides produces a characteristic dark brown color if cerium is present.