Palladium: the essentials
Palladium is a steel-white metal, does not tarnish in air, and is the least dense and lowest melting of the platinum group metals. When annealed, it is soft and ductile. Cold working increases its strength and hardness. It is used in some watch springs.
Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM).
At room temperatures the metal has the unusual property of absorbing up to 900 times its own volume of hydrogen. Hydrogen readily diffuses through heated palladium and this provides a means of purifying the gas.
- Name: palladium
- Symbol: Pd
- Atomic number: 46
- Relative atomic mass (Ar): 106.42 (1) [see note g]
- Standard state: solid at 298 K
- Colour: silvery white metallic
- Classification: Metallic
- Group in periodic table: 10
- Group name: Precious metal or Platinum group metal
- Period in periodic table: 5
- Block in periodic table: d-block
- Electron shell structure: 2.8.18.18.0
- CAS Registry ID: 7440-05-3
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Palladium: historical information
William Hyde Wollaston discovered palladium in 1803-4 in crude platinum ore from South America. He dissolved the ore in aqua regia (a mixture of hydrochloric and nitric acids), neutralised the acid with sodium hydroxide (NaOH), and precipitated the platinum by treatment with ammonium chloride, NH4Cl, as ammonium chloroplatinate. Palladium was then removed as palladium cyanide by treatment with mercuric cyanide. The metal was produced from this cyanide by heating.
Palladium around us Read more »
Palladium has no biological role. Palladium chloride was formerly prescribed as a treatment for tuberculosis at the rate of 0.065 g per day (approximately 1 mg kg-1) without too many bad side effects.
Palladium is found as the free metal associated with platinum and other platinum group metals in Australia, Brazil, Russia, Ethiopia, and North and South America, as well as with nickel and copper deposits (from which it is recovered commercially) in Canada and South Africa.
| Location | ppb by weight | ppb by atoms | Links |
|---|---|---|---|
| Universe | 2 | 0.02 | 
|
| Crustal rocks | 6.3 | 1 | 
|
| Human | (no data) ppb by weight | (no data) atoms relative to C = 1000000 | 
|
Physical properties Read more »
Density of solid: 12023 kg m-3
Molar volume: |196| cm3
Thermal conductivity: |206| W m‑1 K‑1
Heat properties Read more »
Melting point: 1828.05 [1554.9 °C (2830.82 °F)] K
Boiling point: 3236 [2963 °C (5365 °F)] K
Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of palladium is: ccp (cubic close-packed).
Palladium: orbital properties Read more »
Palladium atoms have 46 electrons and the shell structure is 2.8.18.18.0. The ground state electronic configuration of neutral Palladium is [Kr].4d10 and the term symbol of Palladium is 1S0.
Pauling electronegativity: 2.20 (Pauling units)
First ionisation energy: 804.4 kJ mol‑1
Second ionisation energy: 1870 kJ mol‑1
Isolation
Isolation: it would not normally be necessary to make a sample of palladium in the laboratory as the metal is available commercially. The industrial extraction of palladium is complex as the metal occurs in ores mixed with other metals such as platinum. Sometimes extraction of the precious metals such as platinum and palladium is the main focus of a partiular industrial operation while in other cases it is a byproduct. The extraction is complex and only worthwhile since palladium is the basis of important catalysts in industry.
Preliminary treatment of the ore or base metal byproduct with aqua regia (a mixture of hydrochloric acid, HCl, and nitric acid, HNO3) gives a solution containing complexes of gold and platinum as well as H2PdCl4. The gold is removed from this solution as a precipitate by treatment with iron chloride (FeCl2). The platinum is precipitated out as (NH4)2PtCl6 on treatment with NH4Cl, leaving H2PdCl4 in solution. The palladium is precipitated out by treatment with ammonium hydroxide, NH4OH, and HCl as the complex PdCl2(NH3)2. This yields palladium metal by burning.
Palladium isotopes Read more »
Pd-104 is used for the production of radioactive Pd-103 seeds which are used to fight prostate cancer. Pd-103 can also be made from Pd-102. Other Pd isotopes such as Pd-110 and Pd-108 have been used in physical experiments such as research into the decay of Nd-137 and nuclear fusion phenomena. Pd-108 can also be used for the production of radioactive Pd-109 which is used for cancer therapy.
| Isotope | Mass /Da |
Natural abund. (atom %) |
Nuclear spin (I) |
Nuclear magnetic moment (μ/μN) |
|---|---|---|---|---|
| 102Pd | 101.905634 (5) | 1.02 (1) | 0 | |
| 104Pd | 103.904029 (6) | 11.14 (8) | 0 | |
| 105Pd | 104.905079 (6) | 22.33 (8) | 5/2 | -0.642 |
| 106Pd | 105.903478 (6) | 27.33 (3) | 0 | |
| 108Pd | 107.903895 (4) | 26.46 (9) | 0 | |
| 110Pd | 109.905167 (20) | 11.72 (9) | 0 |
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