Terbium

Symbol: Tb
Atomic number: 65
Category: lanthanides
Group: n/a
Period: 6
Block: f
Atomic weight: 158.92535 g/mol
Electrons per shell: 2, 8, 18, 27, 8, 2
CAS number: 7440-27-9
Phase: solid
Density: 8.23 kg/dm³ (near room temperature)
Melting point: 1629 K (1356 °C, 2473 °F)
Boiling point: 3503 K (3230 °C, 5846 °F)
Crystal structure: hexagonal
Oxidation states: 3, 4
Electronegativity: 1.2 (Pauling scale)
Name's origin: terbia
Name's meaning: when the mineral yttria was partitioned into three fractions, the 'terbia' was the fraction that contained the pink color (due to what now is known as erbium)
Facts:
- is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife
- is reasonably stable in air (it does not tarnish after nineteen months at room temperature)
- two crystal allotropes exist, with a transformation temperature of 1289 °C
- is used to dope calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures
- is also used in alloys and in the production of electronic devices
- is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite
- the richest current commercial sources of terbium are the ion-adsorption clays of southern China
- can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible - calcium and tantalum impurities can be removed by vacuum remelting
- as with the other lanthanides, terbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail