Lanthanum is a metallic element, atomic number 57, with the symbol La. It is a silvery white malleable, ductile metal which oxidizes rapidly in air. It belongs to group 3 of the periodic table and is the first element in the lanthanide series, hence the series name. Usually found in rare-earth minerals in combination with cerium and other rare earth elements of the series. It is one of the most reactive of the rare-earth metals. Lanthanum has use in electronic devices rocket propellants, pyrophoric alloys, lighting, camera and telescope lenses, water treatment products, and petroleum cracking catalysts and phosphors in x-ray screens.