Praseodymium

Notable Characteristics

Praseodymium is a soft silvery metallic element, and belongs to the lanthanide group. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, 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 plastic or glass.

Applications

Uses of praseodymium:

• As an alloying agent with magnesium to create high-strength metals that are used in aircraft engines.
• Praseodymium forms the core of carbon arc lights which are used in the motion picture industry for studio[?] lighting and projector[?] lights.
• Praseodymium compounds are used to give glasses and enamels[?] a yellow color.
• Praseodymium is a component of didymium[?] glass, which is used to make certain types of welder's and glass blower[?]'s goggles.

History

The name Praseodymium comes from the Greek prasios, meaning green, and didymos, or twin.

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 C. F. Auer von Welsbach[?] separated didymium into two elements, Praseodymium and Neodymium, which gave salts of different colors.

Biological Role

Praseodymium has no known biological role.

Occurrence

Praseodymium 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.

Compounds

Praseodymium compounds include:

• Fluorides
  • PrF₂[?]
  • PrF₃[?]
  • PrF₄[?]
• Chlorides
  • PrCl₃[?]
• Bromides[?]
  • PrBr₃[?]
  • Pr₂Br₅[?]
• Iodides[?]
  • PrI₂[?]
  • PrI₃[?]
  • Pr₂I₅[?]
• Oxides
  • PrO₂[?]
  • Pr₂O₃[?]
• Sulfides[?]
  • PrS[?]
  • Pr₂S₃[?]
• Selenides[?]
  • PrSe[?]
• Tellurides
  • PrTe[?]
  • Pr₂Te₃[?]
• Nitrides[?]
  • PrN[?]

Isotopes

Naturally occurring praseodymium is composed of one stable isotope, 141-Pr. 38 radioisotopes have been characterized with the most stable being 143-Pr with a half-life of 13.57 days and 142-Pr with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lifes that are less than 5.985 hours and the majority of these have half lifes that are less than 33 seconds. This element also has 6 meta states with the most stable being 138m-Pr (t_½ 2.12 hours), 142m-Pr (t_½ 14.6 minutes) and 134m-Pr (t_½ 11 minutes).

The isotopes of praseodynium range in atomic weight from 120.955 amu (121-Pr) to 158.955 amu (159-Pr). The primary decay mode before the stable isotope, 141-Pr, is electron capture and the primary mode after is beta minus decay. The primary decay products before 141-Pr are element 58 (Cerium) isotopes and the primary products after are element 60 (Neodymium) isotopes.

Precautions

Like all rare earths, praseodymium is of low to moderate toxicity.

External Links

• WebElements.com - Praseodymium (http://www.webelements.com/webelements/elements/text/Pr/index)
• EnvironmentalChemistry.com - Praseodymium (http://environmentalchemistry.com/yogi/periodic/Pr)
• It's Elemental - The Element Praseodymium (http://education.jlab.org/itselemental/ele059)