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Praseodymium - Pr General Information Discovery Praseodymium was first separated from the rare earth didymia by Baron Auer von Welsbach in 1885 in Vienna, Austria. The other component of didymia was neodymium, atomic number 60. Appearance Praseodymium is a soft, malleable, silvery metal. Source Praseodymium occurs along with other rare-earth elements in a variety of minerals, but the two principal commercial sources of most of these elements are monazite and bastnaesite. The usual techniques employed are ion exchange and solvent extraction, although praseodymium is also prepared by calcium reduction of the anhydrous chloride. Uses Praseodymium comprises 5% of the alloy misch metal, which is used in making products such as cigarette lighters. Along with other rare earth elements it is used in carbon arcs for studio lighting and projection. Praseodymium is also a component of didymium glass, used by welders and glassmakers, because it filters out the yellow light present in glass blowing. Salts of this element are used to colour glasses and enamels an intense and unusually clean yellow. Biological Role Praseodymium has no known biological role, and low toxicity. General Information Praseodymium reacts rapidly with water and slowly with oxygen to give a green oxide coating. It is stored under paraffin or sealed in plastic. |
| Physical Information | |||
| Atomic Number | 59 | ||
| Relative Atomic Mass (12C=12.000) | 140.91 | ||
| Melting Point/K | 1204 | ||
| Boiling Point/K | 3785 | ||
| Density/kg m-3 | 6773 (293K) | ||
| Ground State Electron Configuration | [Xe]4f36s2 | ||
| Electron Affinity(M-M-)/kJ mol-1 | 50 |
| Key Isotopes | ||||||
| nuclide | 141Pr | 142Pr | 143Pr | |||
| atomic mass | 140.91 | |||||
| natural abundance | 100% | 0% | 0% | |||
| half-life | stable | 19.2 h | 13.59 days |
| Other Information | ||
| Enthalpy of Fusion/kJ mol-1 | 11.3 | |
| Enthalpy of Vaporisation/kJ mol-1 | 357 | |
| Oxidation States | ||
| main | PrIII | |
| others | PrIV | |
| Covalent Bonds /kJ mol-1 | ||
| not applicable | ||
| Ionisation Energies/kJ mol-1 | ||
| M - M+ | 523.1 | |
| M+ - M2+ | 1018 | |
| M2+ - M3+ | 2086 | |
| M3+ - M4+ | 3761 | |
| M4+ - M5+ | 5543 | |
| M5+ - M6+ | ||
| M6+ - M7+ | ||
| M7+ - M8+ | ||
| M8+ - M9+ | ||
| M9+ - M10+ | ||
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