Terbium

Atomic Symbol: Tb
Group: Lanthanide
Atomic number: 65
Atomic weight: 158.925 amu
CAS registry ID: 7440-27-9
Standard State: Solid at room temperature
Boiling Point: 3073 K
Melting Point: 1633.2 K
Density at 293 K: 8.27 g/mL
Atomic radius: 1.59 covalent, 1.77 Radius of Metals
Electron configuration: [Xe]4f⁹6s²
Electronegativity: 1.22 pauling scale
First Ionization Energy: 564.6 kJ/mol
Heat of Vaporization: 330.9 kJ/mol
Heat of Fusion: 10.8 kJ/mol
Specific Heat: 0.18 J/gK
Heat Atomization: 389 kJ/mole atoms
Thermal Conductivity: 11.1 J/m-sec-deg
Electrical Conductivity: 8.8 1/mohm-cm
Polarizability: 25.5 A^3
Shells: 2,8,18,27,8,2
Discovery: 1843 by Mosander, named after the town of Ytterby in Sweden

Properties
Terbium, like other rare earth elements, should be handled with caution as little is known of its toxicity. It is a silver-gray metal, malleable and ductile. It is soft enough to be cut with a knife and reasonably stable in air (it does not tarnish rapidly). Twenty one isotopes are recognized with atomic masses ranging from 145 to 165. The oxide is a dark chocolate color and is a weak base.

Production and Uses
Terbium is found in cerite, gadolinite, monazite and other minerals that commonly contain traces of rare earth elements. It is isolated using ion-exchange techniques for separation, and is commonly produced by reducing the anhydrous chloride or fluoride (TbF3) with calcium metal in a tantalum crucible.

2TbF3 + 3Ca ---> 2Tb + 3CaF2

Impurities can then be removed by vacuum remelting.

Few uses have been discovered for Terbium. Sodium terbium borate is used in solid-state devices. The oxide may be able to be used as an activator for green phosphors used in color TV tubes. It can be used with ZrO2 as a crystal stabilizer of fuel cells at high temperatures. Some minor use in lasers and semiconductor devices.

Terbium costs about thirty to one hundred dollars per gram.

Sources:
http://pearl1.lanl.gov/periodic/elements/65.html
http://chemlab.pc.maricopa.edu/periodic/Tb.html
http://www.chemicool.com/elements/terbium.html

Ter"bi*um (?), n. [NL., fr. Ytterby, in Sweden. See Erbium.] Chem.

A rare metallic element, of uncertain identification, supposed to exist in certain minerals, as gadolinite and samarskite, with other rare ytterbium earth. Symbol Tr or Tb. Atomic weight 150.

© Webster 1913.