Atomic Number: 46
Atomic Weight: 106.42
Discovery: William Wollaston 1803 (England)
Electron Configuration: [Kr] 4d10
Word Origin: Palladium was named for the asteroid Pallas, which was discovered approximately the same time (1803). Pallas was the Greek goddess of wisdom.
Properties: Palladium has a melting point of 1554°C, boiling point of 2970°C, specific gravity of 12.02 (20°C), and valence of 2, 3, or 4. It is a steel-white metal which does not tarnish in air. Palladium has the lowest melting point and density of the platinum metals. Annealed palladium is soft and ductile, but it becomes much stronger and harder through coldworking. Palladium is attacked by nitric acid and sulfuric acid. At room temperature, the metal can absorb up to 900 times its own volume of hydrogen. Palladium can be beaten into leaf as thin as 1/250,000 of an inch.
Uses: Hydrogen readily diffuses through heated palladium, so this method is often used to purify the gas. Finely divided palladium is used as a catalyst for hydrogenation and dehydrogenation reactions. Palladium is used as an alloying agent and for making jewelry and in dentistry. White gold is an alloy of gold which has been decolorized by the addition of palladium. The metal is also usd to make surgical instruments, electrical contacts, and watches.
Sources: Palladium is found with other metals of the platinum group and with nickel-copper deposits.
Element Classification: Transition Metal
Density (g/cc): 12.02
Melting Point (K): 1825
Boiling Point (K): 3413
Appearance: silvery-white, soft, malleable and ductile metal
Atomic Radius (pm): 137
Atomic Volume (cc/mol): 8.9
Covalent Radius (pm): 128
Ionic Radius: 65 (+4e) 80 (+2e)
Specific Heat (@20°C J/g mol): 0.244
Fusion Heat (kJ/mol): 17.24
Evaporation Heat (kJ/mol): 372.4
Debye Temperature (K): 275.00
Pauling Negativity Number: 2.20
First Ionizing Energy (kJ/mol): 803.5
Oxidation States: 4, 2, 0
Lattice Structure: Face-Centered Cubic
Lattice Constant (Å): 3.890
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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