Lanthanum
Chemical element
Lanthanum is a chemical element; it has symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. Wikipedia
Symbol: La
Atomic number: 57
Electron configuration: [Xe] 5d¹ 6s²
Atomic mass: 138.90547 u
Melting point: 1,688°F (920°C)
Discoverer: Carl Gustaf Mosander
Discovered: 1839