A hard, durable, silvery-white metallic element that is used to form high-temperature alloys with platinum and is plated on other metals to produce a durable corrosion-resistant coating. Atomic number 45; atomic weight 102.905; melting point 1,964°C; boiling point 3,695°C; specific gravity 12.41 (20°C); valence 2, 3, 4, 5, 6. See Periodic Table.