|Boiling Point: 3785oK, 3512oC, 6354oF
Melting Point: 1204oK, 931oC, 1708oF
Electrons Energy Level: 2, 8, 18, 21, 8, 2
Isotopes: 38 + 1 Stable + 5 meta states
Heat of Vaporization: 296.8 Kj/mol
Heat of Fusion: 6.89 kJ/mol
Density: 6.77 g/cm3 @ 300oK
Specific Heat: 0.192 J/gK
Atomic Radius: 2.67Å
Ionic Radius: 1.013Å
Electronegativity: 1.13 (Pauling), 1.07 (Allrod Rochow)
1s2 2s2p6 3s2p6d10 4s2p6d10f3 5s2p6 6s2
The name praseodymium comes from the Greek prasios, meaning green, and didymos, or twin. Praseodymium is frequently misspelled as Praseodynium.
In 1841, Mosander extracted the rare earth didymium from lanthana. In 1874, Per Teodor Cleve concluded that didymium was in fact two elements, and in 1879, Lecoq de Boisbaudran isolated a new earth, samarium, from didymium obtained from the mineral samarskite. In 1885, the Austrian chemist baron Carl Auer Von Welsbach separated didymium into two elements, praseodymium and neodymium, which gave salts of different colors.
It was prepared in relatively pure form in 1931. Ion-exchange and solvent extraction techniques have led to much easier isolation of the rare earths and the cost has dropped greatly. Praseodymium can be prepared by several methods, such as by calcium reduction of the anhydrous chloride of fluoride.
Today, praseodymium is primarily obtained through an ion exchange process from monazite sand, (Ce, La, Th, Nd, Y)PO4, a material rich in rare earth elements.
Pure praseodymium is silvery-white and fairly soft. It oxidizes slowly in air and reacts vigorously with water to release hydrogen gas. It is used as an alloying agent along with magnesium for parts in aircraft engines. Misch metal is 5% praseodymium and is used for alloying steel and in flints used to create sparks in lighters. The glass in welder's goggles contains a mixture of praseodymium and neodymium.
It is somewhat more resistant to corrosion in air than europium, lanthanum, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air, exposing more metal to oxidation. For this reason, praseodymium should be stored under a light mineral oil or sealed in glass.
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.
Praseodymium is available in small quantities in Earths crust (9.5 ppm). It is found in the rare earth minerals monazite and bastnasite, and can be recovered from bastnasite or monazite by an ion exchange process.
Praseodymium also makes up about 5% of Misch metal.
Uses of praseodymium:
Praseodymium compounds include:
Naturally occurring praseodymium is composed of one stable isotope, 141Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143Pr with a half-life of 13.57 days and 142Pr with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than 5.985 hours and the majority of these have half lives that are less than 33 seconds. This element also has six meta states with the most stable being 138mPr (t½ 2.12 hours), 142mPr (t½ 14.6 minutes) and 134mPr (t½ 11 minutes).
The isotopes of praseodymium range in atomic weight from 120.955 (121Pr) to 158.955 (159Pr). The primary decay mode before the stable isotope, 141Pr, is electron capture and the primary mode after is beta minus decay. The primary decay products before 141Pr are element Cerium-58 isotopes and the primary products after are element Neodymium-60 isotopes.
Like all rare earths, praseodymium is of low to moderate toxicity. Praseodymium has no known biological role. As with other rare-earth metals it should be kept under a light mineral oil or sealed in plastic.
Atomic Radius (Å): 2.67Å
Electrochemical Equivalents: 1.7524 g/amp-hr
Atomic Mass Average:
Fusion Heat: 11.3 kJ/mol