PTL:Terbium
From ChemEd Collaborative
| Symbol: | Tb |
|---|---|
| Atomic Number: | 65 |
| Atomic Weight: | 158.92534(2) |
| Electron Configuration: | [Xe] 4f9 6s2 |
| Atomic Radius: | 178.2pm |
| Melting Point: | 1356°C |
| Boiling Point: | 3230°C |
| Heat of Fusion: | 10.8kJ/mol |
| Heat of Vaporization: | 330.9kJ/mol |
| Specific Heat Capacity: | 0.18J/gK |
Terbium is a member of the lanthanide series of elements, which stretches from lanthanum (La) through lutetium (Lu).
Contents |
Discovered
Although it is one of the least abundant lanthanides in the earth's crust, it was discovered relatively early - in 1843. Mosander, the discoverer of other elements (Y, La, and Er), decided to try to again study the oxide yttria. This oxide is a mixture of several others: ceria (cerium oxide); lanthana (lanthanum oxide); and didymia (a mixture of the oxides of praseodymium and neodymium). Mosander separated these from the yttria, and, in the portion that remained, he discovered two new oxides: a yellow oxide he called erbia and a rose-colored oxide he named terbia. From erbia he found the new element erbium, and the new element terbium came from terbia. In a single experiment Mosander found two as yet undiscovered elements.
Characteristics
The metal is soft and silvery. It has a higher density (8.23 g/cc) than any of the preceding lanthanides. In the solid state, the metal has a hexagonal closest packed structure.
Prepared
Like many of the lanthanide elements, terbium is obtained from the mineral monazite [(Ce,Y,La,Nd,Th)PO4], a mixture of the phosphates of Ca, Th, Ce, and most of the other lanthanides.
The metal is obtained by reducing a halide with an "active" metal such as Ca or Li.
3 Li(s) + TbCl3(s) 
Tb(s) + 3 LiCl(s)
Reactions
The reaction is carried out in a tantalum crucible at high temperature in a helium atmosphere (the latter being used to prevent oxidation of the metal).
The metal is also reactive, forming Tb(III) salts on reaction with acids.
Uses
The element is used in [steel] alloys and, as the oxide, in [fluorescent bulbs]. Terbium also has applications as a doping agent in lasers and solid state devices.
Emission Spectra
This is the emission spectra for Terbium.
