History and Production
From Greek prasios and didymos, meaning green and twin. It was discovered in didymia, a mixture of rare earth oxides by C.A. von Welsbach in 1885 via repeat fractional
crystallizations. Nowadays, its compounds are isolated from monazite and bastnaesite via solvent extraction and ion-exchange techniques. The metal can be isolated by the reduction of its fluoride with calcium metal.
Prasodymium is used among other rare earths for the misch metal to make flints for cigarette lighters. With magnesium, for high-strength jet-engine parts. It is also used as carbon arc in motion picture industry.
It is soft, silvery in appearance and is both malleable and ductile. It reacts slowly in air to give a green flaky oxide coating. It is subsequently best kept sealed or under a mineral oil. It is usually distrbuted
(9.1 ppm of earth's crust) in monazite and bastnaesite.
Interatomic distance: 364 pm
Melting point: 931°C
Boiling point: 3520°C
Thermal conductivity/Wm-1K-1: 12.5 (27°C)
Density/kgm-3: 6773 (20°C)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: 355.6 kJ/mol
Gibbs free energy of formation: 320.9 kJ/mol
Entropy: 189.8 J/mol K
Heat capacity: 21.4 J/mol K
Electronic configuration: [Xe] 4f8 6s2
Term symbol: 4I9/2
Electron affinity: - Electronegativity (Pauline): 1.13
Ionization energy (first, second, third): 527.196, 1017.92, 2086.40 kJ/mol