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| Praseodymium | ||||||||||||||||||||||||||||
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| Pronunciation | /ˌpreɪziːəˈdɪmiəm/[1] | |||||||||||||||||||||||||||
| Appearance | grayish white | |||||||||||||||||||||||||||
| Standard atomic weight Ar°(Pr) | ||||||||||||||||||||||||||||
| Praseodymium in the periodic table | ||||||||||||||||||||||||||||
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| Atomic number (Z) | 59 | |||||||||||||||||||||||||||
| Group | f-block groups (no number) | |||||||||||||||||||||||||||
| Period | period 6 | |||||||||||||||||||||||||||
| Block | f-block | |||||||||||||||||||||||||||
| Electron configuration | [Xe] 4f3 6s2 | |||||||||||||||||||||||||||
| Electrons per shell | 2, 8, 18, 21, 8, 2 | |||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||
| Phase at STP | solid | |||||||||||||||||||||||||||
| Melting point | 1204 K (931 °C, 1708 °F)[4] | |||||||||||||||||||||||||||
| Boiling point | 3403 K (3130 °C, 5666 °F) | |||||||||||||||||||||||||||
| Density (at 20° C) | 6.773 g/cm3 [4] | |||||||||||||||||||||||||||
| when liquid (at m.p.) | 6.50 g/cm3 | |||||||||||||||||||||||||||
| Heat of fusion | 6.89 kJ/mol | |||||||||||||||||||||||||||
| Heat of vaporization | 331 kJ/mol | |||||||||||||||||||||||||||
| Molar heat capacity | 27.20 J/(mol·K) | |||||||||||||||||||||||||||
Vapor pressure
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| Atomic properties | ||||||||||||||||||||||||||||
| Oxidation states | common: +3 0,[5] +1,[6] +2,? +4,? +5 | |||||||||||||||||||||||||||
| Electronegativity | Pauling scale: 1.13 | |||||||||||||||||||||||||||
| Ionization energies |
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| Atomic radius | empirical: 182 pm | |||||||||||||||||||||||||||
| Covalent radius | 203±7 pm | |||||||||||||||||||||||||||
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| Other properties | ||||||||||||||||||||||||||||
| Natural occurrence | primordial | |||||||||||||||||||||||||||
| Crystal structure | double hexagonal close-packed (dhcp) (hP4) | |||||||||||||||||||||||||||
| Lattice constants |  c = 1.18328 nm (at 20 °C)[4] | |||||||||||||||||||||||||||
| Thermal expansion | 4.5×10−6/K (at 20 °C)[4][a] | |||||||||||||||||||||||||||
| Thermal conductivity | 12.5 W/(m⋅K) | |||||||||||||||||||||||||||
| Electrical resistivity | poly: 0.700 µΩ⋅m (at r.t.) | |||||||||||||||||||||||||||
| Magnetic ordering | paramagnetic[7] | |||||||||||||||||||||||||||
| Molar magnetic susceptibility | +5010.0×10−6 cm3/mol (293 K)[8] | |||||||||||||||||||||||||||
| Young's modulus | 37.3 GPa | |||||||||||||||||||||||||||
| Shear modulus | 14.8 GPa | |||||||||||||||||||||||||||
| Bulk modulus | 28.8 GPa | |||||||||||||||||||||||||||
| Speed of sound thin rod | 2280 m/s (at 20 °C) | |||||||||||||||||||||||||||
| Poisson ratio | 0.281 | |||||||||||||||||||||||||||
| Vickers hardness | 250–745 MPa | |||||||||||||||||||||||||||
| Brinell hardness | 250–640 MPa | |||||||||||||||||||||||||||
| CAS Number | 7440-10-0 | |||||||||||||||||||||||||||
| History | ||||||||||||||||||||||||||||
| Discovery | Carl Auer von Welsbach (1885) | |||||||||||||||||||||||||||
| Isotopes of praseodymium | ||||||||||||||||||||||||||||
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Praseodymium is a chemical element; it has symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air.
Praseodymium always occurs naturally together with the other rare-earth metals. It is the sixth-most abundant rare-earth element and fourth-most abundant lanthanide, making up 9.1 parts per million of the Earth's crust, an abundance similar to that of boron. In 1841, Swedish chemist Carl Gustav Mosander extracted a rare-earth oxide residue he called didymium from a residue he called "lanthana", in turn separated from cerium salts. In 1885, the Austrian chemist Carl Auer von Welsbach separated didymium into two elements that gave salts of different colours, which he named praseodymium and neodymium. The name praseodymium comes from the Ancient Greek πράσινος (prasinos), meaning 'leek-green', and δίδυμος (didymos) 'twin'.
Like most rare-earth elements, praseodymium most readily forms the +3 oxidation state, which is the only stable state in aqueous solution, although the +4 oxidation state is known in some solid compounds and, uniquely among the lanthanides, the +5 oxidation state is attainable in matrix-isolation conditions. The 0, +1, and +2 oxidation states are rarely found. Aqueous praseodymium ions are yellowish-green, and similarly, praseodymium results in various shades of yellow-green when incorporated into glasses. Many of praseodymium's industrial uses involve its ability to filter yellow light from light sources.
- ^ "praseodymium". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ "Standard Atomic Weights: Praseodymium". CIAAW. 2017.
- ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (4 May 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
- ^ a b c d Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
- ^ Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (15 December 2003). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
- ^ Chen, Xin; et al. (13 December 2019). "Lanthanides with Unusually Low Oxidation States in the PrB3– and PrB4– Boride Clusters". Inorganic Chemistry. 58 (1): 411–418. doi:10.1021/acs.inorgchem.8b02572. PMID 30543295. S2CID 56148031.
- ^ Jackson, M. (2000). "Magnetism of Rare Earth" (PDF). The IRM quarterly. 10 (3): 1.
- ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
- ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
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