Palladium: Least Dense Of The Platinum Group Metals
Palladium is a rare precious metal characterized by its lustrous silvery-white appearance. It was discovered by the English chemist William Hyde Wollaston in London, England in 1803, along with his discovery (together with Smithson Tennant, another English chemist) of the other metals in the platinum group. The name "palladium" was coined by Wollaston from the asteroid named "Pallas".
Of the different precious metals in the platinum group (which includes iridium, platinum, osmium, rhodium, and ruthenium), palladium is known to be the least dense. It likewise has the lowest melting point.
Palladium is utilized in many applications because of its unique properties, some of which are provided below.
Chemical Symbol: Pd
Atomic Number: 46
Category (as an element): Transition Metal
Group/ Period/ Block (in the Periodic Table): 10/ 5/ d
Atomic Weight: 106.42 g.mol-1
Electron Configuration: [Kr] 4d10
Density (near room temperature): 12.023 g.cm-3
Liquid Density (at melting point): 10.38 g.cm-3
Melting Point: 1554.9°C, 2830.82°F, 1828.05°K
Boiling Point: 2963°C, 5365°F, 3236°K
Heat of Fusion: 16.74 kJ.mol-1
Heat of Vaporization: 362 kJ.mol-1
Oxidation States: 0, +1, +2, +4, +6
Electronegativity: 2.2 (Pauling scale)
Atomic Radius: 137 picometre
Covalent Radius: 139±6 picometre
Van der Waals Radius: 163 picometre
Ionization Energies: 804.4 kJ.mol-1 (first), 1870 kJ.mol-1 (second), 3177 kJ.mol-1 (third)
Palladium is used in the following:
1. Catalytic converters;
2. Jewelry and watch making;
3. Dentistry and surgical instruments;
4. Aircraft spark plugs;
5. Electrical contacts;
6. Connector platings;
7. Manuscript illumination.
Since the late 1930s, palladium has been utilized as a precious metal in jewelry. Because of its naturally white properties, palladium has been used as an alternative to white gold. Along with silver and nickel, palladium is popularly used in making white gold alloys.
According to the British Geological Survey (BGS), the top four palladium-producing countries in the world are Russia, South Africa, Canada, and the United States (in this order). Russia produces at least half of the total amount of palladium produced in the world.
Commercially, palladium is produced from copper-nickel deposits in Siberia, South Africa, and in Ontario in Canada. The precious metal is also found - alloyed with the other metals in the platinum group as well as with gold - in Ethiopia, Australia, North and South America, and in the Ural Mountains in Russia.
The Norilsk Nickel Mining and Metallurgical Company in northern Russia is the largest single producer of palladium in the world. Significant amounts of mineable palladium are also found in two other places: the Lac des Ξles igneous complex in northwestern Ontario, Canada and the Stillwater igneous complex in the state of Montana in the United States.
Such is the rarity and preciousness of palladium that many metric tons of ore have to be processed to obtain just a troy ounce of the precious metal. The ISO currency codes of palladium, as a commodity, are XPD and 964. Its price is approximately 150 U.S. dollars per troy ounce.
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