Difference between revisions of "Praseodymium" - New World Encyclopedia
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− | '''Praseodymium''' (chemical symbol '''Pr''', [[atomic number]] 59) is a soft silvery [[metal]]lic element that belongs to the [[lanthanide]] group. | + | '''Praseodymium'''<ref>Praseodymium is frequently misspelled as Praseody'''n'''ium.</ref> (chemical symbol '''Pr''', [[atomic number]] 59) is a soft silvery [[metal]]lic element that belongs to the [[lanthanide]] group. |
== Occurrence == | == Occurrence == | ||
− | |||
− | Praseodymium also makes up about 5% of [[ | + | 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 == | + | == 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, [[Austria]]n [[chemist]] Baron [[Carl Auer von Welsbach]] separated didymium into two elements that gave [[salt]]s of different [[color]]s. These two elements were praseodymium and [[neodymium]]. | |
− | + | The name ''praseodymium'' comes from a combination of two [[Greece|Greek]] words: ''prasios'', meaning "green," and ''didymos'', or "twin." | |
== Notable characteristics == | == Notable characteristics == |
Revision as of 23:47, 21 February 2007
- For other meanings of the abbreviation Pr, see PR.
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General | ||||||||||||||||||||||||||||
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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) | |||||||||||||||||||||||||||
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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 | ||||||||||||||||||||||||||||
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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 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.
Isotopes
Naturally occurring praseodymium is composed of one stable isotope, 141Pr. Thirty-eight 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-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 states with the most stable being 138mPr (t½ 2.12 hours), 142mPr (t½ 14.6 minutes) and 134mPr (t½ 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.
Compounds
Praseodymium compounds include:
- Fluorides
- Chlorides
- Bromides
- Iodides
- Oxides
- 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 (PrNi5) 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.
ReferencesISBN 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
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