Palladium is the chemical element with symbol Pd and atomic number 46. It is a rare, silvery-white platinum-group metal with excellent catalytic activity, corrosion resistance and an unusual ability to absorb hydrogen.
Palladium quick facts
| Property | Value |
| Symbol | Pd |
| Atomic number | 46 |
| Relative atomic mass | 106.42 |
| Group | 10 |
| Period | 5 |
| Block | d-block |
| Density | 12.0 g/cm³ |
| Melting point | 1554.8°C |
| Boiling point | 2963°C |
| Electron configuration | [Kr] 4d¹⁰ |
| Common oxidation states | +2, +4 |
| CAS number | 7440-05-3 |
| Key natural isotope | ¹⁰⁶Pd |
Position and chemistry
Palladium is in group 10, period 5 and the d-block. Its ground-state electron configuration is unusual: [Kr] 4d¹⁰, with no 5s electron in the commonly accepted configuration. Palladium chemistry is dominated by +2, with +4 and other states also important.
See the complete CleverlySmart periodic table.
Physical and catalytic properties
Palladium is ductile, malleable and resistant to corrosion. Its surface efficiently adsorbs hydrogen and many organic molecules, making palladium an outstanding catalyst for reactions involving hydrogenation, dehydrogenation, carbon-carbon bond formation and exhaust-gas treatment.
Palladium can absorb substantial amounts of hydrogen into its crystal lattice. This unusual property has made palladium important in hydrogen purification, sensing and research.
Important palladium compounds
- Palladium chloride (PdCl₂): a common precursor for palladium catalysts and coordination compounds.
- Palladium acetate: widely used as a catalyst precursor in organic synthesis.
- Organopalladium complexes: central to coupling reactions used to build pharmaceuticals, electronic materials and fine chemicals.
Occurrence and production
Palladium occurs with other platinum-group metals and in nickel-copper sulfide ores. It is usually recovered as a by-product of nickel, copper or platinum mining and refining. Because deposits are geographically concentrated and refining is complex, palladium supply can be sensitive to market and geopolitical changes.
Uses of palladium
- Automotive catalytic converters: one of palladium’s largest uses; it helps convert carbon monoxide, hydrocarbons and nitrogen oxides into less harmful gases.
- Chemical catalysis: palladium catalysts are essential to many industrial and pharmaceutical reactions.
- Electronics: used in contacts, multilayer ceramic capacitors and specialised components.
- Jewellery: palladium is used directly and as an alloying metal in some white gold and platinum-group jewellery.
- Hydrogen purification: heated palladium membranes can selectively allow hydrogen to diffuse through.
Palladium isotopes
Natural palladium contains six stable isotopes: ¹⁰²Pd, ¹⁰⁴Pd, ¹⁰⁵Pd, ¹⁰⁶Pd, ¹⁰⁸Pd and ¹¹⁰Pd. Palladium-106 is the most abundant. Several radioactive palladium isotopes are produced in fission or for research.
For broader isotope data, see the CleverlySmart isotope table.
Biological role and safety
Palladium has no known essential biological role. Bulk metal is relatively inert, but soluble palladium compounds can cause irritation or sensitisation and should be handled with normal chemical controls. Fine powders may present fire or inhalation hazards.
Discovery and name
English chemist William Hyde Wollaston discovered palladium in 1803 while refining platinum. He named it after Pallas, an asteroid discovered shortly before.
Frequently asked questions
Why is palladium used in catalytic converters?
Its surface accelerates oxidation and reduction reactions that convert harmful exhaust gases at practical temperatures.
Is palladium a precious metal?
Yes. Palladium is a rare platinum-group metal traded as a precious metal and used in jewellery and investment products.
Palladium in catalytic converters and synthesis
Palladium is one of the key metals in automotive catalytic converters. It helps transform carbon monoxide and unburned hydrocarbons into less harmful products and can participate in reactions that reduce nitrogen-oxide emissions, depending on catalyst design and exhaust conditions.
In organic chemistry, palladium catalysts enable powerful carbon–carbon bond-forming reactions such as Suzuki, Heck and related cross-coupling reactions. These methods are widely used to build pharmaceuticals, agrochemicals and advanced materials.
Hydrogen absorption and materials science
Palladium can absorb substantial amounts of hydrogen into its crystal lattice. This property makes palladium and palladium alloys useful in hydrogen purification membranes, sensors and research on hydrogen storage and catalysis.
Frequently asked questions
Why is palladium so expensive?
It is rare, supply is concentrated, and demand from automotive catalysts, electronics and chemical industries can be large relative to annual production.
Is palladium used in jewellery?
Yes. It is used on its own and as a component of white-gold and platinum-family jewellery alloys because it is corrosion-resistant and relatively light for a platinum-group metal.
