Atomic Number: 46
Atomic Symbol: Pd
Atomic Weight: 106.42
Melting Point: 2,830.8 F (1,554.9 C) |
Boiling Point: 5,365.4 F (2,963 C)
Word origin: Palladium was named after the asteroid Pallas, which was discovered around the same time. The asteroid was named for Pallas Athena, the Greek goddess of wisdom.
Discovery: William Hyde Wollaston, an English chemist, discovered palladium in 1803.
Properties of palladium
Palladium is a transition metal. It is silvery white and does not tarnish in air. It has the lowest density and lowest melting point of any member of the platinum group. It can be attacked by nitric and sulfuric acid. [See Periodic Table of the Elements]
It is soft and ductile when annealed (heated and then cooled slowly). Cold-working greatly increases its strength and hardness.
Palladium has the unusual property of absorbing up to 900 times its own volume of hydrogen when at room temperatures. It can then possibly form the compound palladium hydride (Pd2H); it is not yet known if this is a true compound. Hydrogen easily diffuses through heated palladium, which purifies the gas.
Sources of palladium
Along with other metals in the platinum group, palladium deposits are found in Russia, South and North America, Ethiopia and Australia. It is also found in copper-nickel deposits in Ontario and South Africa. The state of separation and isolation process from the other platinum metals depends on the type of ore in which palladium is found.
Uses of palladium
The most well-known use of palladium is as part of white gold. White gold is gold with palladium added, which leads to its decoloration. It is a popular metal for jewelry.
Like gold, palladium can be beaten into leaf as thin as 1/250,000th of an inch. This is used in dentistry instruments, watches, surgical instruments and electrical contacts.
Finely divided palladium is a good catalyst. It is often used for hydrogenation and dehydrogenation reactions because hydrogen readily diffuses through heated palladium.
(Source: Los Alamos National Laboratory)