Praseodymium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

59 cerium ← praseodymium → neodymium - ↑ Pr ↓ Pa Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	praseodymium, Pr, 59
Chemical series	lanthanides
Group, Period, Block	n/a, 6, f
Appearance	grayish white
Atomic mass	140.90765 (2) g/mol
Electron configuration	[Xe] 4f3 6s2
Electrons per shell	2, 8, 18, 21, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	6.77 g·cm−3
Liquid density at m.p.	6.50 g·cm−3
Melting point	1208  K (935 ° C, 1715 ° F)
Boiling point	3793 K (3520 ° C, 6368 ° F)
Heat of fusion	6.89 kJ·mol−1
Heat of vaporization	331 kJ·mol−1
Heat capacity	(25 °C) 27.20 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 1771 1973 (2227) (2571) (3054) (3779)
Atomic properties
Crystal structure	hexagonal
Oxidation states	3 (mildly basic oxide)
Electronegativity	1.13 (Pauling scale)
Ionization energies ( more)	1st: 527 kJ·mol−1
	2nd: 1020 kJ·mol−1
	3rd: 2086 kJ·mol−1
Atomic radius	185 pm
Atomic radius (calc.)	247 pm
Miscellaneous
Magnetic ordering	no data
Electrical resistivity	( r.t.) (α, poly) 0.700 µΩ·m
Thermal conductivity	(300 K) 12.5 W·m−1·K−1
Thermal expansion	( r.t.) (α, poly) 6.7 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 2280 m/s
Young's modulus	(α form) 37.3 GPa
Shear modulus	(α form) 14.8 GPa
Bulk modulus	(α form) 28.8 GPa
Poisson ratio	(α form) 0.281
Vickers hardness	400 MPa
Brinell hardness	481 MPa
CAS registry number	7440-10-0
Selected isotopes
Main article: Isotopes of praseodymium iso NA half-life DM DE ( MeV) DP 141Pr 100% Pr is stable with 82 neutrons 142Pr syn 19.12 h β- 2.162 142Nd ε 0.745 142Ce 143Pr syn 13.57 d β- 0.934 143Nd
References

Praseodymium ( IPA: /ˌpreɪziə(ʊ)ˈdɪmiəm, ˌpreɪsi-/) is a chemical element in the periodic table that has the symbol Pr and atomic number 59.

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 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 colour.
• Praseodymium is a component of didymium glass, which is used to make certain types of welder's and glass blower's goggles.
• Dr. Matthew Sellars of the Laser Physics Centre at the Australian National University in Canberra, Australia slowed down a light pulse to a few hundred meters per second using praseodymium mixed with silicate crystal.

History

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.

Occurrence

Praseodymium is available in small quantities in Earth’s crust (9,5ppm). 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.

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, ¹⁴¹Pr. 38 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-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 ^138mPr (t_½ 2.12 hours), ^142mPr (t_½ 14.6 minutes) and ^134mPr (t_½ 11 minutes).

The isotopes of praseodymium range in atomic weight from 120.955 u (¹²¹Pr) to 158.955 u (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 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. Praseodymium has no known biological role.