Praseodymium

Praseodymium, ₅₉Pr
Praseodymium
Pronunciation	/ˌpreɪziːəˈdɪmiəm/ (PRAY-zee-ə-DIM-ee-əm)
Appearance	grayish white
Standard atomic weight Ar°(Pr)
	140.90766±0.00001; 140.91±0.01 (abridged);
Praseodymium in the periodic table
	cerium ← praseodymium → neodymium
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)
Boiling point	3403 K (3130 °C, 5666 °F)
Density (at 20° C)	6.773 g/cm3
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)
Atomic properties
Oxidation states	0, +1, +2, +3, +4, +5 (a mildly basic oxide)
Electronegativity	Pauling scale: 1.13
Ionization energies	1st: 527 kJ/mol ; 2nd: 1020 kJ/mol ; 3rd: 2086 kJ/mol ; ;
Atomic radius	empirical: 182 pm
Covalent radius	203±7 pm
	Spectral lines of praseodymium
Other properties
Natural occurrence	primordial
Crystal structure	double hexagonal close-packed (dhcp) (hP4)
Lattice constants	a = 0.36723 nm; c = 1.18328 nm (at 20 °C)
Thermal expansion	4.5×10−6/K (at 20 °C)
Thermal conductivity	12.5 W/(m⋅K)
Electrical resistivity	poly: 0.700 µΩ⋅m (at r.t.)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+5010.0×10−6 cm3/mol (293 K)
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 v; e;
ε	142Ce
	Category: Praseodymium; view; talk; edit; \| references

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 PrB^3– and PrB^4– 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.

Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

[1] "praseodymium". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)

[2] "Standard Atomic Weights: Praseodymium". CIAAW. 2017.

[CIAAW2021-3] 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.

[Arblaster_2018-4] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[Cloke1993-5] 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.

[6] Chen, Xin; et al. (13 December 2019). "Lanthanides with Unusually Low Oxidation States in the PrB^3– and PrB^4– Boride Clusters". Inorganic Chemistry. 58 (1): 411–418. doi:10.1021/acs.inorgchem.8b02572. PMID 30543295. S2CID 56148031.

[jackson-8] Jackson, M. (2000). "Magnetism of Rare Earth" (PDF). The IRM quarterly. 10 (3): 1.

[9] Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

[NUBASE2020-10] 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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