Praseodymium Facts - Element 59

Praseodymium Properties, History, and Uses

Praseodymium is one of the rare earth elements.
Praseodymium is one of the rare earth elements. Science Picture Co / Getty Images

Praseodymium is element 59 on the periodic table with the element symbol Pr. It's one of the rare earth metals or lanthanides. Here is a collection of interesting facts about praseodymium, including its history, properties, uses, and sources.

  • Praseodymium was discovered by Swedish chemist Carl Mosander in 1841, but he did not purify it. He was working on rare earth samples, which contain elements with such similar properties they are extremely hard to separate from each other. From a crude cerium nitrate sample, he isolated an oxide he called "lantana", which was lanthanum oxide. Lantana turned out to be a mixture of oxides. One fraction was a pink fraction he called didymium. Per Teodor Cleve (1874) and Lecoq de Boisbaudran (1879) determined didymium was a mixture of elements. In 1885, Austrian chemist Carl von Welsbach separated didymium into praseodymium and neodymium. Credit for the official discovery and isolation of element 59 is generally given to von Welsbach.
  • Praseodymium gets it name from the Greek words prasios, which means "green", and didymos, which means "twin". The "twin" part refers to the element being the twin of neodymium in didymium, while "green" refers to the color of the salt isolated by von Welsbach. Praseodymium forms Pr(III) cations, which are yellowish green in water and glass.
  • In addition to the +3 oxidation state, Pr also occurs in +2, +4, and (unique for a lanthanide) +5. Only the +3 state occurs in aqueous solutions.
  • Praseodymium is a soft silver-colored metal that develops a green oxide coating in air. This coating peels or spalls off, exposing fresh metal to oxidation. To prevent degradation, pure praseodymium is typically stored under a protective atmosphere or in oil.
  • Element 59 is highly malleable and ductile. Praseodymium is unusual in that it is paramagnetic at all temperatures above 1 K. Other rare earth metals are ferromagnetic or antiferromagnetic at low temperatures.
  • Natural praseodymium consists of one stable isotope, praseodymium-141. 38 radioisotopes are known, the most stable being Pr-143, which has a half-life of 13.57 days. Praseodymium isotopes range from mass number 121 to 159. 15 nuclear isomers are also known.
  • Praseodymium occurs naturally in the Earth's crust at an abundance of 9.5 parts per million. It accounts for about 5% of the lanthanides found in the minerals monazite and bastnasite. Seawater contains 1 part per trillion of Pr. Essentially no praseodymium is found in the Earth's atmosphere.
  • The rare earth elements have many uses in modern society and are considered extremely valuable. Pr gives a yellow color to glass and enamel. Around 5% of mischmetal consists of praseodymium. The element is used with other rare earths to make carbon arc lights. It colors cubic zirconia yellow-green and may be added to simulated gemstones to mimic peridot. Modern firesteel contains about 4% praseodymium. Didymium, which contains Pr, is used to make glass for protective eyewear for welders and glass blowers. Pr is alloyed with other metals to made powerful rare earth magnets, high strength metals, and magnetocaloric materials. Element 59 is used as a doping agent to make fiber optic amplifiers and to slow light pulses. Praseodymium oxide is an important oxidation catalyst.
  • Praseodymium serves no known biological function. Like other rare earth elements, Pr exhibits low to moderate toxicity to organisms.

Praseodymium Element Data

Element Name: Praseodymium

Element Symbol: Pr

Atomic Number: 59

Element Group: f-block element, lanthanide or rare earth

Element Period: period 6

Atomic Weight: 140.90766(2)

Discovery: Carl Auer von Welsbach (1885)

Electron Configuration: [Xe] 4f3 6s2

Melting Point: 1208 K ​(935 °C, ​1715 °F)

Boiling Point: 3403 K ​(3130 °C, ​5666 °F)

Density: 6.77 g/cm3 (near room temperature)

Phase: solid

Heat of Fusion: 6.89 kJ/mol

Heat of Vaporization: 331 kJ/mol

Molar Heat Capacity: 27.20 J/(mol·K)

Magnetic Ordering: paramagnetic

Oxidation States: 5, 4, 3, 2

Electronegativity: Pauling scale: 1.13

Ionization Energies:

1st: 527 kJ/mol
2nd: 1020 kJ/mol
3rd: 2086 kJ/mol

Atomic Radius: 182 picometers

Crystal Structure: double hexagonal close-packed or DHCP

References:

Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110.

Emsley, John (2011). Nature's Building Blocks.

Gschneidner, K.A., and Eyring, L., Handbook on the Physics and Chemistry of Rare Earths, North Holland Publishing Co., Amsterdam, 1978.

R. J. Callow, The Industrial Chemistry of the Lanthanons, Yttrium, Thorium and Uranium, Pergamon Press, 1967.

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Helmenstine, Anne Marie, Ph.D. "Praseodymium Facts - Element 59." ThoughtCo, Jan. 23, 2017, thoughtco.com/praseodymium-facts-element-59-4125194. Helmenstine, Anne Marie, Ph.D. (2017, January 23). Praseodymium Facts - Element 59. Retrieved from https://www.thoughtco.com/praseodymium-facts-element-59-4125194 Helmenstine, Anne Marie, Ph.D. "Praseodymium Facts - Element 59." ThoughtCo. https://www.thoughtco.com/praseodymium-facts-element-59-4125194 (accessed November 18, 2017).