Quick Facts
| Property | Value |
|---|---|
| Symbol | Pd |
| Atomic Number | 46 |
| Atomic Mass | 106.42 u |
| Category | Transition Metal |
| Period | 5 |
| Group | 10 |
| Block | d |
| Electron Configuration | [Kr] 4d¹⁰ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 12.023 g/cm³ |
| Melting Point | 1554.9°C (1828.05 K) |
| Boiling Point | 2963°C (3236 K) |
| Appearance | Silvery-white, lustrous metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Kr] 4d¹⁰ |
| Electronegativity | 2.20 (Pauling scale) |
| First Ionization Energy | 804.4 kJ/mol |
| Atomic Radius | 137 pm |
| Covalent Radius | 139 pm |
| Van der Waals Radius | 163 pm |
History and Discovery
Discovered by: William Hyde Wollaston Year of Discovery: 1803 Location: London, England
Etymology
Named after the asteroid Pallas (discovered in 1802), which was itself named after Pallas Athena, the Greek goddess of wisdom.
Discovery Story
William Hyde Wollaston discovered palladium in 1803 while analyzing crude platinum ore from South America. He initially sold it anonymously, offering it for sale through a London shop. Richard Chenevix claimed it was a platinum-mercury alloy, but Wollaston eventually revealed himself as the discoverer.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹⁰²Pd | 1.02% | Stable | - |
| ¹⁰⁴Pd | 11.14% | Stable | - |
| ¹⁰⁵Pd | 22.33% | Stable | - |
| ¹⁰⁶Pd | 27.33% | Stable | - |
| ¹⁰⁸Pd | 26.46% | Stable | - |
| ¹¹⁰Pd | 11.72% | Stable | - |
Occurrence
Natural Abundance
Palladium is rare, comprising about 0.015 ppm of Earth's crust. It is found in platinum ores, nickel-copper sulfide deposits, and placer deposits. Major producers are Russia, South Africa, Canada, and the United States.
Extraction and Production
- Byproduct: From platinum and nickel-copper mining
- Refining: Chemical separation from other metals
- Sources: Russia and South Africa dominate
- Global production: about 210 tons annually
Applications and Uses
Automotive Catalysts
- Catalytic converters (main use—about 85%)
- Reduces CO, hydrocarbons, and NOx emissions
- Increasingly preferred over platinum
Electronics
- Multi-layer ceramic capacitors (MLCCs)
- Connectors and contacts
- Dental alloys
Chemical Industry
- Hydrogenation catalysts
- Fuel cells (hydrogen storage)
- Cross-coupling reactions (Suzuki, Heck)
Other Uses
- Jewelry (white gold alloys)
- Dental fillings and crowns
- Hydrogen purification
- Investment (palladium coins and bars)
Biological Role
Palladium has no known biological role and is not essential for any organism.
In the Human Body
Palladium is not normally present in the body. It may be present in dental alloys.
Medical Uses
Palladium-103 is used in brachytherapy for prostate cancer treatment.
Safety and Hazards
Toxicity
Palladium metal is considered non-toxic. Some palladium compounds can cause allergic reactions in sensitive individuals.
Handling Precautions
- Generally safe to handle
- Palladium salts can cause allergic contact dermatitis
- Dust may irritate respiratory system
- Standard precious metal handling procedures
Environmental Impact
Palladium is released from catalytic converters. It accumulates in roadside soils but at very low concentrations.
Interesting Facts
- Palladium can absorb up to 900 times its own volume of hydrogen gas
- It was the central element in the controversial "cold fusion" claims of 1989
- Palladium prices have exceeded gold prices in recent years
- The electron configuration [Kr] 4d¹⁰ is anomalous (no 5s electrons)
- Palladium was secretly sold by Wollaston before he revealed his discovery