Praseodymium - Pr
Chemical properties of praseodymium - Health effects of praseodymium - Environmental effects of praseodymium
|Atomic mass||140.91 g.mol -1|
|Electronegativity according to Pauling||1.1|
|Density||6.8 g.cm-3 at 20°C|
|Melting point||931 °C|
|Boiling point||3512 °C|
|Ionic radius||0.101 nm (+3)|
|Electronic shell||[ Xe ] 4f3 6s2|
|Energy of first ionisation||522 kJ.mol -1|
|Energy of second ionisation||1016 kJ.mol -1|
|Energy of third ionisation||2082.4 kJ.mol -1|
|Energy of fourth ionisation||3752 kJ.mol -1|
|Energy of fifth ionisation||5534 kJ.mol -1|
|Standard Potential||- 2.47 V|
|Discovered by||von Welsbach in 1885|
Praseodymium is a soft malleable, silvery-yellow metal. It is a member of the lanthanide group of the periodic table of elements. It reacts slowly with oxygen: when exposed to air it forms a green oxide that does not protect it from further oxidation. It is more resistant to corrosion in air the other rare metals, but it still needs to be stored under oil or coated with plastic. It reacts rapidly with water.
A major use of the metal is in a pyrophoric alloy used in cigarettes lighter flints. Praseodymium compounds have different uses: the oxide is used in carbon electrodes for arc lighting, and it is know for its ability to give glass a nice yellow colour. This glass filters out the infrared radiation, so it is used in the goggles which protect the eyes of welders. The salts are used to colour enamel and glass. Praseodymium can be used as alloying agent with magnesium to create high strenght metals that are used in aircraft engines.
Praseodymium is one of the rare chemicals, that can be found in houses in equipment such as colour televisions, fluorescent lamps, energy-saving lamps and glasses. All rare chemicals have comparable properties. The use of praseodymium is still growing, due to the fact that it is suited to produce catalysers and to polish glass.
Praseodymium in the environment
Praseodymium is one of the more abundant of rare-earth elements. It is four time more abundant than tin. Praseodymium is usually found only in two different kinds of ores.
The major commercial ores in which praseodymium is found are monazite and bastnasite. The main mining areas are China, USA, Brazil, India, Sri Lanka and Australia. Reserves of praseodymium are estimated to be around 2 million tonnes. World production of praseodymium is about 2500 tonnes per year.
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