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| Atomic symbol: Pr |
| Atomic number: 59 |
| Atomic weight: 140.9077 |
| Atomic volume: 20.8 cm3/mol |
| Density: 6.77 g/cm3 |
| Period Number: 6 |
| Group number: none |
| Group name: Rare Earth, Lanthanides |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 1204.2 K |
| Boiling point: 3293 K |
| Heat of fusion: 6.890 kJ/mol |
| Heat of vaporization: 296.80 kJ/mol |
| Ionization Energy: 5.464 eV |
| 1st ionization energy: 523.2 kJ/mole |
| 2nd ionization energy: 1018 kJ/mole |
| 3rd ionization energy: 2086 kJ/mole |
| Electronegativity: 1.13 |
| Electron affinity: 50 kJ/mole |
| Specific heat: 0.19 J/gK |
| Heat atomization: 356 kJ/mole atoms |
| Shells: 2,8,18,21,8,2 |
| Electron Shell Configuration: [Xe] 4f3 6s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 4 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 3 |
Appearance & Characteristics |
| Structure:: cp: close packed (ABCB) |
| Color: silvery-white |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: soft |
| Uses: alloys, Welder's mask |
| Reaction with air: vigorous, =>Pr6O11 approx |
| Reaction with 6M HCl: mild, =>H2, PrCl3 |
| Reaction with 15M HNO3: mild, =>Pr(NO3)3 |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 1 |
| Oxide(s): PrO2 Pr6O11 |
| Hydride(s): PrH2 PrH3 |
| Chloride(s): PrCl3 |
| Atomic Radius: 182 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): pm |
| Ionic radius (3+ ion): 113 pm |
| Thermal conductivity: 12.5 J/m-sec-deg |
| Electrical conductivity: 14.706 1/mohm-cm |
| Polarizability: 28.2 A^3 |
| Source: Monazite(phosphate),bastnaesite |
| Relative abundance solar system: -0.778 log |
| Abundance earth's crust: 0.9 log |
| Estimated crustal abundance: 9.2 milligrams per kilogram |
| Estimated oceanic abundance: 6.4×10-7 milligrams per liter |
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| (Gr. prasios, green, and didymos, twin) In 1841 Mosander extracted the rare earth didymia from lanthana; in 1879, Lecoq de Boisbaudran isolated a new earth, samaria, from didymia obtained from the mineral samarskite. Six years later, in 1885, von Welsbach separated didymia into two others, praseodymia and neodymia, which gave salts of different colors. As with other rare earths, compounds of these elements in solution have distinctive sharp spectral absorption bands or lines, some of which are only a few Angstroms wide. |
| The element occurs along with other rare-earth elements in a variety of minerals. Monazite and bastnasite are the two principal commercial sources of the rare-earth metals. It was prepared in relatively pure form in 1931. |
| Praseodymium is soft, silvery, malleable, and ductile. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that falls off when exposed to air. As with other rare-earth metals, it should be kept under a light mineral oil or sealed in plastic. |
| Misch metal, used in making cigarette lighters, contains about 5% praseodymium metal. The rare-earth oxides, including Pr2O3 are among the most refractory substances known. Along with other rare earths, it is widely used as a core material for carbon arcs used by the motion picture industry for studio lighting and projection. Salts of praseodymium are used to color glasses and enamels; when mixed with certain other materials, praseodymium produces an intense and unusually clean yellow color in glass. Didymium glass, of which praseodymium is a component, is a colorant for welders goggles. |
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