Palladium

Palladium, ₄₆Pd
Palladium
Pronunciation	/pəˈleɪdiəm/ (pə-LAY-dee-əm)
Appearance	silvery white
Standard atomic weight Ar°(Pd)
	106.42±0.01; 106.42±0.01 (abridged);
Palladium in the periodic table
	rhodium ← palladium → silver
Atomic number (Z)	46
Group	group 10
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d10
Electrons per shell	2, 8, 18, 18
Physical properties
Phase at STP	solid
Melting point	1828.05 K (1554.9 °C, 2830.82 °F)
Boiling point	3236 K (2963 °C, 5365 °F)
Density (at 20° C)	12.007 g/cm3
when liquid (at m.p.)	10.38 g/cm3
Heat of fusion	16.74 kJ/mol
Heat of vaporization	358 kJ/mol
Molar heat capacity	25.98 J/(mol·K)
Atomic properties
Oxidation states	common: 0, +2, +4; +1, +3, +5
Electronegativity	Pauling scale: 2.20
Ionization energies	1st: 804.4 kJ/mol ; 2nd: 1870 kJ/mol ; 3rd: 3177 kJ/mol ; ;
Atomic radius	empirical: 137 pm
Covalent radius	139±6 pm
Van der Waals radius	163 pm
	Spectral lines of palladium
Other properties
Natural occurrence	primordial
Crystal structure	face-centered cubic (fcc) (cF4)
Lattice constant	a = 389.02 pm (at 20 °C)
Thermal expansion	11.77×10−6/K (at 20 °C)
Thermal conductivity	71.8 W/(m⋅K)
Electrical resistivity	105.4 nΩ⋅m (at 20 °C)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+567.4×10−6 cm3/mol (288 K)
Young's modulus	121 GPa
Shear modulus	44 GPa
Bulk modulus	180 GPa
Speed of sound thin rod	3070 m/s (at 20 °C)
Poisson ratio	0.39
Mohs hardness	4.75
Vickers hardness	400–600 MPa
Brinell hardness	320–610 MPa
CAS Number	7440-05-3
History
Naming	after asteroid Pallas, itself named after Pallas Athena
Discovery and first isolation	William Hyde Wollaston (1802)
Isotopes of palladium v; e;
γ	–
	Category: Palladium; view; talk; edit; \| references

Palladium is a chemical element; it has symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1802 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas (formally 2 Pallas), which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). They have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.

More than half the supply of palladium and its congener platinum is used in catalytic converters, which convert as much as 90% of the harmful gases in automobile exhaust (hydrocarbons, carbon monoxide, and nitrogen dioxide) into nontoxic substances (nitrogen, carbon dioxide and water vapor). Palladium is also used in electronics, dentistry, medicine, hydrogen purification, chemical applications, groundwater treatment, and jewelry. Palladium is a key component of fuel cells, in which hydrogen and oxygen react to produce electricity, heat, and water.

Ore deposits of palladium and other PGMs are rare. The most extensive deposits have been found in the norite belt of the Bushveld Igneous Complex covering the Transvaal Basin in South Africa; the Stillwater Complex in Montana, United States; the Sudbury Basin and Thunder Bay District of Ontario, Canada; and the Norilsk Complex in Russia. Recycling is also a source, mostly from scrapped catalytic converters. The numerous applications and limited supply sources result in considerable investment interest.

^ "Standard Atomic Weights: Palladium". CIAAW. 1979.
^ 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 Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^ Pd(I) is known in [Pd₂]²⁺ compounds; see Christoph Fricke; Theresa Sperger; Marvin Mendel; Franziska Schoenebeck (2020). "Catalysis with Palladium(I) Dimers". Angewandte Chemie International Edition. 60 (7). doi:10.1002/anie.202011825.
^ Pd(III) has been observed; see Powers, D. C.; Ritter, T. (2011). "Palladium(III) in Synthesis and Catalysis" (PDF). Higher Oxidation State Organopalladium and Platinum Chemistry. Topics in Organometallic Chemistry. Vol. 35. pp. 129–156. Bibcode:2011hoso.book..129P. doi:10.1007/978-3-642-17429-2_6. ISBN 978-3-642-17428-5. PMC 3066514. PMID 21461129. Archived from the original (PDF) on 12 June 2013.
^ Palladium(V) has been identified in complexes with organosilicon compounds containing pentacoordinate palladium; see Shimada, Shigeru; Li, Yong-Hua; Choe, Yoong-Kee; Tanaka, Masato; Bao, Ming; Uchimaru, Tadafumi (2007). "Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms". Proceedings of the National Academy of Sciences. 104 (19): 7758–7763. doi:10.1073/pnas.0700450104. PMC 1876520. PMID 17470819.
^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
^ 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.

[1] "Standard Atomic Weights: Palladium". CIAAW. 1979.

[CIAAW2021-2] 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_2018-3] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[4] Pd(I) is known in [Pd₂]²⁺ compounds; see Christoph Fricke; Theresa Sperger; Marvin Mendel; Franziska Schoenebeck (2020). "Catalysis with Palladium(I) Dimers". Angewandte Chemie International Edition. 60 (7). doi:10.1002/anie.202011825.

[5] Pd(III) has been observed; see Powers, D. C.; Ritter, T. (2011). "Palladium(III) in Synthesis and Catalysis" (PDF). Higher Oxidation State Organopalladium and Platinum Chemistry. Topics in Organometallic Chemistry. Vol. 35. pp. 129–156. Bibcode:2011hoso.book..129P. doi:10.1007/978-3-642-17429-2_6. ISBN 978-3-642-17428-5. PMC 3066514. PMID 21461129. Archived from the original (PDF) on 12 June 2013.

[6] Palladium(V) has been identified in complexes with organosilicon compounds containing pentacoordinate palladium; see Shimada, Shigeru; Li, Yong-Hua; Choe, Yoong-Kee; Tanaka, Masato; Bao, Ming; Uchimaru, Tadafumi (2007). "Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms". Proceedings of the National Academy of Sciences. 104 (19): 7758–7763. doi:10.1073/pnas.0700450104. PMC 1876520. PMID 17470819.

[7] Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

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

[NUBASE2020-9] 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.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]