Palladium
Symbol: Pd
Atomic Number: 46
Atomic Mass: 106.42 amu (atomic mass units)
Melting Point: 1552.0 C (1825.15 K, 2825.6 F)
Boiling Point: 2927.0 C (3200.15 K, 5300.6 F)
Number of Protons: 46
Number of Electrons: 46
Number of Neutrons: 60
Classification: Transition Metal
Group name: Precious metal or Platinum Group Metal (PGM)
Crystal Structure: Cubic
Density @ 293 K: 12.02 grams per cubic centimeter
Color: white
Palladium was discovered by the English chemist William Hyde Wollaston in 1803. He was working on a sample of platinum ore from South America. Having dissolved the ore in aqua regia (a mixture of nitric and hydrochloric acids) he then neutralized the solution with sodium hydroxide. The platinum was precipitated out of solution with ammonium chloride. Treating the remaining solution with mercuric cyanide precipitated out palladium cyanide. The pure metal was recovered by heating the palladium cyanide.
Palladium is a member of the Platinum Group Metals (PGM) the other members of this group are platinum, rhenium, ruthenium, osmium and rhodium. Of all the PGM palladium is the least dense and has the lowest melting point.
Palladium metal will not tarnish in air and like gold it can be beaten into a very thin leaf.
The metal has the very interesting and valuable ability to absorb up to 900 times its own volume of hydrogen at room temperature.
While palladium has no biological role palladium chloride was used in the treatment of tuberculosis. Modern antibiotics now provide a more effective and safer treatment so this practice has ceased.
The element has six naturally occurring stable isotopes the most abundant of which is palladium-106 at 27.33%. The other stable isotopes are palladium-102 (1.02%), palladium-104 (11.14%), palladium-105 (22.33%), palladium-108 (26.46%) and palladium-110 (11.72%). In addition nearly forty unstable isotopes of palladium have been produced.
Palladium is a rare element but is found in the ores of a number of metals including platinum, gold, nickel, copper and silver. Its production is as a by-product from the extraction of these other metals.
Palladium has a number of industrial uses.
* White gold is gold which has been decolorized by the addition of palladium.
* When finely divided palladium is used as a catalyst in both hydrogenation and dehydrogenation processes.
* Heated palladium is used in the purification of hydrogen.
* Palladium alloys are used in jewelry manufacturing.
* It is used to make dental crowns.
* Palladium is used in the manufacturing of surgical instruments and watches.
* Palladium chloride can absorb carbon monoxide this has led to its usage in carbon monoxide detectors.
