Difference between revisions of "Praseodymium" - New World Encyclopedia

Vapor pressure
59	cerium ← praseodymium → neodymium
	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/cm³
Liquid density at m.p.	6.50 g/cm³
Melting point	1208 K; (935 °C, 1715 °F)
Boiling point	3793 K; (3520 °C, 6368 °F)
Heat of fusion	6.89 kJ/mol
Heat of vaporization	331 kJ/mol
Heat capacity	(25 °C) 27.20 J/(mol·K)
Atomic properties
Crystal structure	hexagonal
Oxidation states	3; (mildly basic oxide)
Electronegativity	1.13 (Pauling scale)
Ionization energies; (more)	1st: 527 kJ/mol
	2nd: 1020 kJ/mol
	3rd: 2086 kJ/mol
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·K)
Thermal expansion	(r.t.) (α, poly); 6.7 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 2280 m/s
Speed of sound (thin rod)	(r.t.) (α form) 37.3 m/s
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
Notable isotopes

Revision as of 00:27, 22 February 2007

For other meanings of the abbreviation Pr, see PR.

Praseodymium^[1] (chemical symbol Pr, atomic number 59) is a soft silvery metallic element that belongs to the lanthanide group.

Occurrence

Praseodymium is available in small quantities in the Earth’s crust—about 9.5 parts per million (ppm). It is found in the rare earth minerals monazite and bastnasite, and it can be recovered from these minerals by an ion exchange process. Praseodymium also makes up about 5% of Mischmetal, an alloy of rare earth elements in a range of naturally occurring proportions.

History and etymology

In 1841, Carl Gustaf Mosander extracted a rare earth called "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, Austrian chemist Baron Carl Auer von Welsbach separated didymium into two elements that gave salts of different colors. These two elements were praseodymium and neodymium.

The name praseodymium comes from a combination of two Greek words: prasios, meaning "green," and didymos, or "twin."

Notable characteristics

Praseodymium is an inner transition metal (or lanthanide) that lies in period 6 of the periodic table, between cerium and neodymium. This element is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium. Nonetheless, when exposed to air, it develops a green oxide coating that spalls off, exposing more metal to oxidation. For this reason, praseodymium should be stored under a light mineral oil or sealed in glass.

Isotopes

Naturally occurring praseodymium is composed of one stable isotope, ¹⁴¹Pr. In addition, many radioisotopes have been characterized. Of these, the longest-lived radioisotopes are ¹⁴³Pr, with a half-life of 13.57 days, and ¹⁴²Pr, with a half-life of 19.12 hours. All the remaining radioactive isotopes have half-lives that are less than 5.985 hours, and most of them have half-lives that are less than 33 seconds. This element also has six meta states.

The isotopes of praseodymium range in atomic weight from 120.955 atomic mass units (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.

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

See also praseodymium compounds.

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.
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.
Praseodymium alloyed with nickel (Pr Ni₅) has such a strong magnetocaloric effect that it has allowed scientists to approach within one thousandth of a degree of absolute zero^[2].

Precautions

Like all rare earths, praseodymium is of low to moderate toxicity. Praseodymium has no known biological role.

Footnotes

↑ Praseodymium is frequently misspelled as Praseodynium.
↑ Emsley, John (2001). NATURE'S BUILDING BLOCKS. Oxford University Press, pp. 342. ISBN 0-1985-0341-5.

References
ISBN links support NWE through referral fees

Praseodymium Los Alamos National Laboratory. Retrieved February 21, 2007.

Chang, Raymond (2006). Chemistry (ninth ed.) New York, NY: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.

Cotton, F. Albert, and Wilkinson, Geoffrey (1980). Advanced Inorganic Chemistry (4th ed.), New York, NY: Wiley. ISBN 0-471-02775-8.

Greenwood, N.N., and Earnshaw, A. (1998). Chemistry of the Elements (2nd Edition). Oxford, UK; Burlington, Massachusetts: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654. Online version.

Jones, Adrian P., Frances Wall, and C. Terry Williams (editors) (1996). Rare Earth Minerals: Chemistry, Origin and Ore Deposits (The Mineralogical Society Series). London, UK: Chapman and Hall. ISBN 0412610302 (ISBN-13: 978-0412610301).

Stwertka, Albert (1998). Guide to the Elements, Revised Edition. Oxford, UK: Oxford University Press. ISBN 0-19-508083-1.

External links

Template:ChemicalSources

Credits

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[1] Praseodymium is frequently misspelled as Praseodynium.

[2] Emsley, John (2001). NATURE'S BUILDING BLOCKS. Oxford University Press, pp. 342. ISBN 0-1985-0341-5.

[1]

[2]

@@ Line 64: / Line 64: @@
 == Notable characteristics ==
-Praseodymium is somewhat more resistant to [[corrosion]] in air than [[europium]], [[lanthanum]], [[cerium]], or [[neodymium]], but it does develop a green [[oxide]] coating that [[spall]]s 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.
+Praseodymium is an [[inner transition metal]] (or lanthanide) that lies in period 6 of the [[periodic table]], between [[cerium]] and [[neodymium]]. This element is somewhat more resistant to [[corrosion]] in air than [[europium]], [[lanthanum]], [[cerium]], or [[neodymium]]. Nonetheless, when exposed to air, it develops a green [[oxide]] coating that [[spall]]s off, exposing more metal to [[oxidation]]. For this reason, praseodymium should be stored under a light [[mineral oil]] or sealed in glass.
 === Isotopes ===
-Naturally occurring praseodymium is composed of one stable [[isotope]], <sup>141</sup>Pr. Thirty-eight [[radioisotope]]s have been characterized with the most stable being <sup>143</sup>Pr with a [[half-life]] of 13.57 days and <sup>142</sup>Pr with a half-life of 19.12 hours. All of the remaining [[radioactive]] isotopes have half-lives that are less than 5.985 hours and the majority of these have half lives that are less than 33 seconds. This element also has six [[meta state]]s with the most stable being <sup>138m</sup>Pr (t<sub>½</sub> 2.12 hours), <sup>142m</sup>Pr (t<sub>½</sub> 14.6 minutes) and <sup>134m</sup>Pr (t<sub>½</sub> 11 minutes).
+Naturally occurring praseodymium is composed of one stable [[isotope]], <sup>141</sup>Pr. In addition, many [[radioisotope]]s have been characterized. Of these, the longest-lived radioisotopes are <sup>143</sup>Pr, with a [[half-life]] of 13.57 days, and <sup>142</sup>Pr, with a half-life of 19.12 hours. All the remaining [[radioactive]] isotopes have half-lives that are less than 5.985 hours, and most of them have half-lives that are less than 33 seconds. This element also has six [[meta state]]s.
-The isotopes of praseodymium range in [[atomic weight]] from 120.955 [[atomic mass unit|u]] (<sup>121</sup>Pr) to 158.955 u (<sup>159</sup>Pr). The primary [[decay mode]] before the stable isotope, <sup>141</sup>Pr, is [[electron capture]] and the primary mode after is [[beta minus decay]]. The primary [[decay product]]s before <sup>141</sup>Pr are element 58 ([[Cerium]]) isotopes and the primary products after are element 60 ([[Neodymium]]) isotopes.
+The isotopes of praseodymium range in [[atomic weight]] from 120.955 [[atomic mass unit]]s (u) (<sup>121</sup>Pr) to 158.955 u (<sup>159</sup>Pr). The primary [[decay mode]] before the stable isotope, <sup>141</sup>Pr, is [[electron capture]] and the primary mode after is [[beta minus decay]]. The primary [[decay product]]s before <sup>141</sup>Pr are element 58 ([[cerium]]) isotopes and the primary products after are element 60 ([[neodymium]]) isotopes.
 == Compounds ==