Praseodymium (Pr)
Stable Isotopes of Praseodymium
| Isotope | Z(p) | N(n) | Atomic Mass | Natural Abundance | Nuclear Spin |
| Pr-141 | 59 | 82 | 140.907648 | 100.00% | 5/2+ |
Praseodymium was discovered in 1885 by Carl F. Auer von Welsbach. It takes its name from the Greek phrase prasios didymos, meaning “green twin.”
A lanthanide-series rare earth element, praseodymium is a pale yellow metal which attains a green oxide coating on exposure to air. It exhibits two crystalline modifications: an alpha form that has a hexagonal close-packed structure, a density of 6.773 g/cm3 and a molar volume of 20.82 cm3/mol; and a beta form that has an open body-centered cubic structure, a density of 6.64 g/cm3 and a molar volume of 21.20 cm3/mol. The alpha form transforms to beta at 792 ºC.
Praseodymium is paramagnetic at ambient temperatures. There are several known compounds. Chloride, bromide and iodide salts are all hygroscopic and soluble in water and alcohol. Praseodymium salts containing oxo anions such as sulfate, hydroxide, carbonate, silicates, oxalate, thiosulfate, chromate, molybdate and borate are also known.
Praseodymium is a component of didymium glass used in welders' goggles. Its salts are used as colorants for glasses and enamels: when in glass, they produce an intense yellow color. Praseodymium's oxide is one of the most refractory substances known and is a core material for carbon arcs used in lighting and projection. A Misch metal that contains about 5% praseodymium is used to make cigarette lighters.
Properties of Praseodymium
| Name | Praseodymium |
| Symbol | Pr |
| Atomic number | 59 |
| Atomic weight | 140.9077 |
| Standard state | Solid at 298° K |
| CAS Registry ID | 7440-10-0 |
| Group in periodic table | N/A |
| Group name | Lanthanoid |
| Period in periodic table | 6 (Lanthanoid) |
| Block in periodic table | f-block |
| Color | Silvery white, yellowish tinge |
| Classification | Metallic |
| Melting point | 931 °C |
| Boiling point | 3512 °C |
| Vaporization point | 3510 ºC |
| Thermal conductivity | 12.5 W/(m·K) at 298.2 °K |
| Electrical resistivity | 68 µΩ·cm at 25 °C |
| Electronegativity | 1.1 |
| Heat of vaporization | 330 kJ·mol-1 at 3512 °C |
| Heat of fusion | 6.9 kJ·mol-1 |
| Density of liquid | 6.50 g/cm3 at 931 °C |
| Density of solid | 6.77 g/cm3 |
| Electron configuration | [Xe]4f36s2 |
| Atomic radius | 1.828 Å |
| First ionization potential | 5.46 eV |
| Oxidation states | +2, +3, +4 |
| Most stable oxidation state | +3 |
