In compounds, the most common oxidation states of manganese are +2, +3, +4, +6, and +7. Manganese(II) oxide, MnO, is the tenth most abundant compound in the Earth's crust (1400 ppm). Potassium permanganate, KMnO4, is a deeply purple crystalline substance when pure, and forms purple solutions when dissolved in water; it is a strong oxidizing agent, and is used in bleaches, disinfectants, deodorizers, and as a reagent for some reactions in organic chemistry. Traces of manganese give amethysts, which are composed primarily of silicon dioxide, their characteristic purple color.
Iron has been used by humans at least as far back as 3500 BC, mostly for ceremonial purposes because of the difficulty in obtaining it in its pure form. The iron that was used in this way was often recovered from meteorites. The processing of smelting iron from its ores was discovered in Asia Minor around 1500 BC. Iron ore from Magnesia in Lydia, Asia Minor, was discovered to attract other pieces of iron; this ore was named "magnetite" and the attractive pieces of metal were named "magnets" after their country of origin.
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Nickel powder or Raney nickel (a nickel-aluminum alloy) are used as catalysts for the production of hydrogenated oils, in which unsaturated fats, which contain carbon-carbon double bonds, and tend to be liquids at room temperature, are reacted with hydrogen gas to produce saturated fats, which contain carbon-carbon single bonds only, and tend to be solids at room temperature. The hydrogen and unsaturated fats are adsorbed onto the surface of the metal, which slightly weakens the hydrogen-hydrogen bonds and the carbon-carbon double bond; when the hydrogen "bumps" against the weakened bond, the hydrogen atoms are added to the carbon-carbon double bond, producing a single bond, and the saturated product drifts away from the metal surface, leaving it free to react with more of the reactants. This process is used in the production of shortening from vegetable oils, and the production of margarines and other spreads.
Rhodium is a silvery, hard, unreactive metal. It is named from the Greek word for rose, rhodon, because of its red-colored salts. It is found in the Earth's crust at a concentration of 0.2 ppb, making it the 78th most abundant element. It is found in some areas as the free metal, and in the ore rhodplumsite [(Rh3Pb2S2)], and is also found in some platinum ores.
Palladium is a soft, malleable and ductile, silvery-white metal. It is found in the Earth's crust at a concentration of 0.6 ppb, making it the 76th most abundant element. It is named after the asteroid, Pallas, which had been discovered in the same year that the metal was first isolated (1802). Palladium is occasionally found as the free metal, and also in the ores stibiopalladinite [palladium antimonide, Pd5Sb2] and braggite [(Pd,Pt,Ni)S], but is most commonly obtained as a by-product of the mining of copper, silver, and gold.
Osmium is a hard, lustrous, blue-gray or blue-black metal. Its name is derived from the Greek word for odor, osme, because of its nasty smell (which is actually caused by osmium tetroxide). It is found in the Earth's crust at a concentration of 0.1 ppb, making it the 79th most abundant element. It is found as the free metal, and in iridosmine and osmiridium, alloys of osmium and iridium that may also contain traces of platinum and rhodium. Osmium is also found in some platinum ores, and is commercially obtained as a by-product from nickel refining.
Iridium is a hard, brittle, silvery-white metal. It is named from the Latin word for "rainbow," iris, because of the colorful compounds that it forms. It is found in the Earth's crust at a concentration of 3 ppt, making it the 82nd most abundant element. It is found as the free metal, and in iridosmine and osmiridium, alloys of iridium and osmium that may also contain traces of platinum and rhodium. Most iridium is obtained as a by-product from the refining of platinum.
Platinum is a very heavy, soft, malleable and ductile, silvery-white metal. It is named from the Spanish word platina, meaning "little silver," because it was first known (to Europeans, anyway) as an unworkable silver-like metal found alongside gold in some deposits. It is found in the Earth's crust at a concentration of 1 ppb, making it the 75th most abundant element. It occurs naturally as the free metal, in an alloy with iridium called platiniridium, and in the ores cooperite [(Pt,Pd,Ni)S] and sperrylite [platinum arsenide, PtAs2]
Because copper resists corrosion by water, air, and most acids (except for concentrated nitric and sulfuric acids), it is ideal for making coins. The US one-cent piece, the penny, used to be made from solid copper (or copper alloyed with tin, nickel, or zinc) but due to the increasing cost of copper, this was replaced in 1982 with a coin made from a zinc core surrounded by a thin copper plating (about 2.4% of the mass of the coin). [An interesting chemical demonstration can be done with these kinds of pennies: if the copper on the edge of the penny is filed off to expose the zinc, and the coin dropped into hydrochloric acid, the zinc will undergo a single-displacement reaction with the hydrochloric acid and dissolve in the solution as soluble zinc chloride, ZnCl2, while the copper on the obverse and reverse sides of the penny will remain unaffected, leaving two thin pieces of copper foil still bearing the impressions of the Lincoln head and the Lincoln Memorial.] The US five-cent piece, the nickel, is an alloy of 75% copper and 25% nickel; and the the ten-cent piece (the dime) and 25-cent piece (the quarter) are 91.67% copper and 8.33% nickel. The US Sacajawea dollar coin, first issued in November of 1999 is also made primarily of copper (88.5% copper, 6% zinc, 3.5% manganese, and 2% nickel).
Copper is used to make several important metal alloys. Bronze is an alloy of copper and tin. Brass is an alloy of copper and zinc, which is addition to being harder than copper can be polished to a high, golden luster. Gunmetal (also known as red brass) is an alloy of copper, tin, and zinc which is strong enough to make guns and cannons. Cupronickel (also called Monel metal) is an alloy of copper and nickel commonly used in coins, such as the US 5-cent piece, and in shipbuilding. Alloys of copper and nickel are also used in desalination plants and underwater pumps because it resists corrosion by sea water. Aluminum bronzes are alloys of copper and up to 7% aluminum that have a gold luster, and are very resistant to corrosion; they are used in naval architecture, engine parts on ships, and landing gear components.
Gold is a soft, malleable, yellow metal. It is an extremely rare element, having a concentration of 1 ppb in the Earth's crust, making it the 73rd most abundant element. The name is derived from the Anglo-Saxon language, while the chemical symbol "Au" is derived from the Latin name for the metal, aurum ("shining dawn"). It is often found as the free element as nuggets or grains, and in alluvial deposits, and is associated with some sulfide ores, and is also found in the mineral sylvanite [silver gold telluride, (Ag,Au)Te2].
Zinc is the fourth most commonly used metal, after iron, aluminum, and copper. Its main use is used to coat ("galvanize") iron or steel, forming a protective layer which is preferentially oxidized instead of the iron. Since 1982, the US one-cent piece has been made of primarily zinc (about 97.6% of a penny's weight), surrounded by a thin coating of copper (see above for the entry on Copper). Zinc is also used in the manufacture of automotive engine parts and car bodies, electrical equipment, and in the making of brass (an alloy of 67% copper and and 33% zinc). Other zinc alloys include nickel silvers (20% zinc, 60% copper, and 20% nickel) that are often used in tableware, and Prestal (78% zinc, 22% aluminum), which is almost as strong as steel, but easy to mold. Zinc forms the anode component of dry cell and alkaline batteries; although they are not rechargeable, they are still commonly used because they are cheap. 2ff7e9595c
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