Praseodymium

Cerium - Praseodymium - Neodymium Pr Pa       Full table
General
Name, Symbol, Number	Praseodymium, Pr, 59
Chemical series	Lanthanides
Group, Period, Block	_ , 6 , f
Density, Hardness	6640 kg/m3, no data
Appearance	silvery white, yellowish tinge
Atomic Properties
Atomic weight	140.90765(2) amu
Atomic radius (calc.)	185 (247) pm
Covalent radius	165 pm
van der Waals radius	no data
Electron configuration	[Xe]6s6s24f3
e- 's per energy level	2, 8, 18, 21, 8, 2
Oxidation states (Oxide)	3 (mildly basic)
Crystal structure	hexagonal
Physical Properties
State of matter	solid
Melting point	1204 K (1707.8 °F)
Boiling point	3793 K (6368 °F)
Molar volume	20.8 ×1010-3 m3/mol
Heat of vaporization	296.8 kJ/mol
Heat of fusion	6.89 kJ/mol
Vapor pressure	1,333224E-06 Pa at 1070 K
Velocity of sound	2280 m/s at 293.15 K
Miscellaneous
Electronegativity	1.13 (Pauling scale)
Specific heat capacity	193 J/(kg*K)
Electrical conductivity	1.48 106/m ohm
Thermal conductivity	12.5 W/(m*K)
1st ionization potential	527 kJ/mol
2nd ionization potential	1020 kJ/mol
3rd ionization potential	2086 kJ/mol
4th ionization potential	3761 kJ/mol
Most Stable Isotopes
iso NA half-life DM DE MeV DP 141Pr 100% 141Pr is stable with 82 neutrons 142Pr {syn.} 19.12 h β- 2.162 MeV 142Nd &epsilon 0.745 MeV 142Ce 143Pr {syn.} 13.57 d β- 0.934 MeV 143Nd
SI units & STP are used except where noted.

Praseodymium is a chemical element in the periodic table that has the symbol Pr and atomic number 59.

Table of contents

1 Notable Characteristics 2 Applications 3 History 4 Biological Role 5 Occurrence 6 Compounds 7 Isotopes 8 Precautions 9 External Links

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.

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

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
• EnvironmentalChemistry.com - Praseodymium
• It's Elemental - The Element Praseodymium