- a rare-earth, metallic element present in certain minerals and yielding colorless salts. Symbol: Tb; atomic number: 65; atomic weight: 158.924; specific gravity: 8.25.
- a soft malleable silvery-grey element of the lanthanide series of metals, occurring in gadolinite and monazite and used in lasers and for doping solid-state devices. Symbol: Tb; atomic no: 65; atomic wt: 158.92534; valency: 3 or 4; relative density: 8.230; melting pt: 1356°C; boiling pt: 3230°C
n. Symbol Tb
- A soft metallic rare-earth element used in x-ray tubes. Atomic number 65.
- A soft, silvery-gray metallic element of the lanthanide series. It is used in color television tubes, x-ray machines, and lasers. Atomic number 65; atomic weight 158.925; melting point 1,356°C; boiling point 3,123°C; specific gravity 8.229; valence 3, 4. See Periodic Table.