What is the X in X-mas?
tantalum tan·ta·lum (tān'tə-ləm)
A hard heavy metallic element that is exceptionally resistant to chemical attack below 150°C and is used to make electronic components and surgical instruments. Atomic number 73; atomic weight 180.948; melting point 3,017°C; boiling point 5,458°C; specific gravity 16.7; valence 2, 3, 4, 5.
A hard, heavy, gray metallic element that is highly resistant to corrosion at low temperatures. It is used to make light-bulb filaments, surgical instruments, and glass for camera lenses. Atomic number 73; atomic weight 180.948; melting point 2,996°C; boiling point 5,425°C; specific gravity 16.6; valence 2, 3, 4, 5. See Periodic Table.