Palladium

Palladium is a chemical element with the chemical symbol PD and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by WIlliam Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.



Softer than platinum, ductile and resistant to oxidation and high temperature corrosion, palladium is useful in eliminating harmful emissions produced by internal combustion engines. Autocatalysts are by far the largest user of palladium; autocatalysts convert over 90 percent of hydrocarbons, carbon monoxide and oxides of nitrogen produced in the exhaust from gasoline engines into carbon dioxide, nitrogen and water vapor

Harmful effects: Palladium is considered to be of low toxicity. Characteristics: Palladium is a rare, lustrous, silvery-white metal. It is malleable and ductile and, like [|gold], palladium can be beaten into thin leaf. It does not tarnish in air but does tarnish lightly in moist air containing [|sulfur]. The metal is strongly resistant to corrosion in air and to the action of acids (except nitric acid) at ordinary temperatures. Palladium is remarkable in its capacity to absorb up to 900 times its own volume of [|hydrogen]. As it absorbs the hydrogen, it expands visibly, like a sponge swelling up when absorbing water.

Uses of Palladium
The largest use of palladium is in catalytic converters for automobiles. Finely divided palladium is used as a catalyst for hydrogenation/dehydrogenation reactions and for petroleum cracking. The metal is used in jewelry, for example in white gold (an alloy of gold decolorized by the addition of palladium). Palladium is used in dentistry, watch making, and in making __surgical instruments__ and electrical contacts. It is also used to purify hydrogen because the gas easily diffuses through heated palladium.
 * finely divided palladium is a good catalyst for hydrogenation and dehydrogenation reactions
 * alloyed for use in jewellery. White gold is an alloy of gold decolourised by the addition of palladium
 * can be beaten into leaf as thin as 1/250000 inch
 * dentistry (crowns)
 * used in fine instruments such as watches and some surgical instruments
 * used to make electrical contacts
 * used to purify hydrogen gas

Palladium primarily exists in the 0, +2, +4 oxidation states; the +4 oxidation state is comparatively rare. One major example of palladium(IV) is hexachloropalladate(IV), [PdCl6]2−. Elemental palladium reacts with chlorine to give palladium(II) chloride; it dissolves in nitric acid and precipitates palladium(II) acetate on addition of acetic acid. These two compounds and the bromide are reactive and relatively inexpensive, making them convenient entry points to palladium chemistry. All three are not monomeric; the chloride and bromide often must be refluxed in acetonitrile to obtain the more reactive acetonitrile __complex__ monomers, for example: PdX 2 + 2 MeCN → PdX 2 (MeCN) 2 (X = Cl, Br)
 * Palladium Compounds**

History: It is a platinum metal aka noble metal. The history of palladium is usually hand in hand with the history of platinum. This is because they are usually found together in some state. Their history starts when we try to separate the two. Once it was discovered the demand grew like crazy. Major sources were found in Russia and South Africa. In the US it has been discovered in Montana.

In 2007, Russia was the top producer of palladium, with a 44% world share, followed by South Africa with 40%. Canada with 6% and the U.S. with 5% are the only other substantial producers of palladium. Palladium can be found as a __free__ metal alloyed with gold and other platinum-group metals in placer deposits of the Ural Mountains, Australia, Ethiopia, North and South America. For the production of palladium these deposits play only a minor role. The most important commercial sources are nickel-copper deposits found in the Sudbury Basin, Ontario, and the Norilsk–Talnakh deposits in Siberia. The other large deposit is the Merensky Reef platinum group metals deposit within the Bushveld Igneous Complex South Africa. The Stillwater igneous complex of Montana and the Roby zone ore body of the Lac des Îles igneous complex of Ontario are the two other sources of palladium in Canada and the United States. Palladium is found in the rare minerals cooperite and polarite. Palladium is also produced in nuclear fission reactors and can be extracted from spent nuclear fuel (see synthesis of precious metals) though this source for palladium is not used. None of the existing nuclear reprocessing facilities are equipped to extract palladium from the high-level radioactive waste.
 * Occurances**

Finely divided palladium metal can be pyrophoric. As a platinum-group metal, the bulk material is quite inert. Although contact dermatitis has been reported, the amount of data on the effects of exposure to palladium is limited. It has been shown that people with an allergic reaction to palladium also react to nickel, making it possible to avoid the use of dental alloys containing palladium on those so allergic. A considerable amount of palladium is distributed by the exhausts of cars with catalytic converters. Between 4 and 108 ng/km of palladium particulate is released by such cars. The total uptake of from food is estimated to be lower than 2 µg per person a day. The second possible source for palladium is alloys for dental restoration, there the possible uptake of palladium is estimated to be lower than 15 µg per person per day. People working with palladium or its compounds might have a considerably higher uptake. For soluble compounds like palladium chloride 99% is eliminated from the body within 3 days.
 * Palladium Precautions**


 * Symbol:** Pd **Atomic Number:** 46 **Atomic Mass:** 106.42 amu **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/Electrons:** 46 **Number of Neutrons:** 60 **Classification:** Transition Metal **Crystal Structure:** Cubic **Density @ 293 K:** 12.02 g/cm3 **Color:** white

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0046.gif width="309" height="307"]] ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Pd-102 || Stable ||
 * Pd-103 || 16.99 days ||
 * Pd-104 || Stable ||
 * Pd-105 || Stable ||
 * Pd-106 || Stable ||
 * Pd-107 || 6500000.0 years ||
 * Pd-108 || Stable ||
 * Pd-109 || 13.5 hours ||
 * Pd-110 || Stable ||

Facts

 * Date of Discovery:** 1803
 * Discoverer:** William Wollaston
 * Name Origin:** From the Greek goddess of wisdom (Pallas) and after an asteroid
 * Uses:** jewelry, medical instruments
 * Obtained From:** platinum, nickel, copper, mercury ores