Praseodymium

Element Name: Praseodymium
Atomic Number: 59
Atomic Mass: 140.90765
Atomic Symbol: Pr
Melting Point: 931° C
Boiling Point: 3520° C

Praseodymium is a rare earth element that is silver in color. It’s ductile, malleable, and soft while being fairly reactive. Unlike a few of the other rare earths, Praseodymium is somewhat resistant to corrosion in air, but the oxide layer it forms does not prevent further oxidation. Praseodymium is unique because of how many valid oxidation states it has. It exists in the +2, +3, and +4 state, but it was recently discovered that it can exist in +5 as well. Its name means “Green Twin”, as it is regarded as the twin element to Neodymium. The element itself is silver, but the “Green” comes from the facts that most of its compounds are distinctly green. Praseodymium-141 is the only isotope found in nature; 38 other radioisotopes exist. Praseodymium is almost always a paramagnet until you reach 1 K – this is unique among the rare earth elements who typically behave as ferromagnets at low temperatures.

Interesting Facts:

Praseodymium’s predecessor, Didymium, was given an atomic symbol on Mendeleev’s first periodic table. Carl Welsbach was not the first to suspect Didymium was made up of more than one element, but he was the first to successfully separate it. He did this via fractional crystallization, wherein each experiment took up to two days and involved more than 100 of these experiments to properly separate neodymium from praseodymium. It has two oxide forms, but only the oxide form using both +3 and +4 is stable in air. When alloyed with nickel, the compound has such a strong magnetocaloric effect (changes temperature when an external magnetic field is applied) that it can approach 0.001 K (one thousandth of a degree above absolute zero).

Sources:

Praseodymium is not present free in nature, but is found in several rare earth minerals. Monazite and bastnaesite make up the most notable sources of it. It occurs at 8.7 ppm on the earth’s surface.

Industrial Uses:

Praseodymium can be used to replace neodymium in neodymium-iron-boron magnets, a high-power magnet which sees widespread use. When paired with its twin, it makes didymium, a material that absorbs yellow light. This material is used in welding glasses. Praseodymium is also used in other glasses to give it a yellow or green hue. It sees similar use in the lighting industry as a phosphor. It is useful in the construction of high-strength aircraft engines when alloyed with magnesium. Misch metal, the flint in lighters and strikers, is around 5% praseodymium.

References:

“Facts About Cerium.” Livescience. Livescience.com, 20 June 2013. Web. 26 July
2016.
“Cerium.” Wikipedia. Wikimedia Foundation, n.d. Web. 26 July 2016.
“Cerium Element Facts / Chemistry.” Chemicool. Chemicool.com, 4 Oct. 2012.
Web. 26 July 2016.
Gray, Theodore W., and Nick Mann. The Elements: A Visual Exploration of Every
Known Atom in the Universe. New York: Black Dog & Leventhal, 2009. Print.