Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid 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.

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Atomic properties

Standard atomic weight106.42 ±0.01
Atomic mass106.421 u

Atomic radii

Radius (empirical)137 pm
Radius (calculated)169 pm
Covalent radius139 ±6 pm
Van der Waals radius163 pm

Atomic shell

Electron configurationKr 4d10
Ionization energy(1st) 8.336839 eV
(2nd) 19.43 eV
(3rd) 32.93 eV
(4th) 46 eV
(5th) 61 eV
Shell model

Physical properties

Density11.99 g·cm−3 (293.1 K)
Molar volume8.56·10-6 m3·mol−1
Speed of sound3,070 m·s−1


Melting point1,828 K
Boiling point3,236 K
Liquid range1,407 K
Transition temperature3.2 K


Melting enthalpy16.7 kJ·mol-1
Enthalpy of vaporization380 kJ·mol-1
Binding energy377 kJ·mol-1

Heat and conductivity

Thermal conductivity72 W·m-1·K-1
Expansion coefficient1.18·10-5 K-1


Mohs hardness4.75
Brinell hardness37.3 NM·m-2
Vickers hardness461 NM·m-2

Elastic properties

Young’s modulus121 GPa
Shear modulus44 GPa
Bulk modulus180 GPa
Poisson’s ratio0.39

Electrical properties

Electrical conductivity9.26·106 S·m-1
Resistance1.08·10-7 Ωm


Magnetic susceptibility5.67·10-4 cm3·mol−1 (288 K)

Optical properties

Reflectivity72 %

Chemical properties

Basicityslightly basic
Oxidation state0, +2, +4
Standard potential0.915 V (Pd2+ + 2e- → Pd)


Pauling scale2.2
Allred-Rochow scale1.35
Ghosh-Gupta scale3.572 eV
Nagle scale1.61
Pearson absolute negativity4.45 eV

Other properties

Natural occurrenceprimordial
Crystal structureFace-centered cubic
Goldschmidt Classificationsiderophile
Superconductorwith transition tempperature under special conditions
Price/kg49,500 USD

Natural abundances

2 ppb ≈ 2.01·1010 M☉
3 ppb ≈ 5.96·109 Mt
670 ppb ≈ 670 mg
Earth’s crust
6.3 ppb ≈ 174 Mt