|
History and Production
Derived from gadolinite, a mineral named after Gadolin, a Finnish chemist. The metal oxide was first discovered by J.C.G. de Marignac and the element was isolated by P.-É. Lecoq de Boisbaudran in 1886.
The main commercial sources are now obtained from monazite and bastnaesite, which contain a mixture of other rare earth metals. Gadolinium salts can be separated using solvent extraction and ion-exchange techniques. The metal can then
be obtained by the reduction of its fluoride with calcium metal. It is used as an alloying agent (~1%) increase the workability and resistance of
chromium and iron to high temperatures and oxidation. Gadolinium compounds are used in making phosphors for color television tubes.
Physical Data
It is silvery-white and quite ductile. It tarnishes in moist air to give a loosely adhereing oxide film. The metal exists in two allotropic forms. The a form is hexagonal close-packed
while the b form, exists above 1235°C, has a body-centered cubic structure.
Gadolinium has the highest absorption cross section for thermal neutrons of any element. The natural abundance is about 6.1 ppm of the earth's crust and is usually associated with other rare earth metals.
Interatomic distance: 357.4 pm
Melting point: 1313°C
Boiling point: 3273°C
Thermal conductivity/Wm-1K-1: 10.6 (27°C)
Density/kgm-3: 7900 (25°C)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: 397.5 kJ/mol
Gibbs free energy of formation: 359.8 kJ/mol
Entropy: 194.3 J/mol K
Heat capacity: 27.5 J/mol K
Electronic data
Electronic configuration: [Xe] 4f7 5d1 6s2
Term symbol: 9D2
Electron affinity: - Electronegativity (Pauline): 1.20
Ionization energy (first, second, third): 593.395, 1166.508, 1990.49 kJ/mol
Chemical properties
| 
