(In iron or plain carbon steels the oxygen actually migrates into the underlying material.) Chromium is usually plated on top of a nickel layer which may or may not have been copper plated first. It forms a compound called a spinal structure which, being very dense, prevents diffusion of oxygen into the underlying layer. Chromium compounds of oxidation state +6 are powerful oxidants.Ĭhromium is passivated by oxygen, forming a thin (usually a few atoms thick being transparent because of thickness) protective oxide surface layer with another element such as nickel, and/or iron. The most common oxidation states of chromium are +2, +3, and +6, with +3 being the most stable. Chromium exhibits a wide range of possible oxidation states. Chromium(0) has an electronic configuration of 4s 13d 5, due to the lower energy of the high spin configuration. (See also chromium minerals)Ĭhromium is obtained commercially by heating the ore in the presence of aluminium or silicon.Ĭhromium is a member of the transition metals, in group 6. This mine is a kimberlite pipe rich in diamonds, and the reducing environment so provided helped produce both elemental chromium and diamond.
The Udachnaya Mine in Russia produces samples of the native metal. Though native chromium deposits are rare, some native chromium metal has been discovered. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa.Īpproximately 15 million tons of marketable chromite ore were produced in 2000, and converted into approximately 4 million tons of ferro-chrome with an approximate market value of 2.5 billion United States dollars. Kazakhstan, India, Russia and Turkey are also substantial producers. About two-fifths of the chromite ores and concentrates in the world are produced in South Africa. Occurrence and production World production trendĬhromium is mined as chromite (FeCr 2O 4) ore. The remainder is used in the chemical industry and refractory and foundry industries.Ĭhromium was named after the Greek word "Chrôma" meaning color, because of the many colorful compounds made from it. Later that year he successfully isolated chromium atoms.ĭuring the 1800s chromium was primarily used as a component of paints and in tanning salts but now metal alloys account for 85% of the use of chromium. He was also able to detect traces of chromium in precious gemstones, such as ruby, or emerald. In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven. He was able to produce chromium oxide with a chemical formula of CrO 3, by mixing crocoite with hydrochloric acid. In 1797, Louis Nicolas Vauquelin received samples of crocoite ore.
A bright yellow made from crocoite became a color in fashion. The use of Siberian red lead as a paint pigment developed rapidly. In 1770, Peter Simon Pallas visited the same site as Lehmann and found a red "lead" mineral that had very useful properties as a pigment in paints. Though misidentified as a lead compound with selenium and iron components, the material was in fact lead chromate with a formula of PbCrO 4, now known as the mineral crocoite. On 26 July 1761, Johann Gottlob Lehmann found an orange-red mineral in the Ural Mountains which he named Siberian red lead. It is also odourless, tasteless, and malleable. It is a steel-gray, lustrous, hard metal that takes a high polish and has a high melting point. Chromium ( Template:PronEng) is a chemical element which has the symbol Cr and atomic number 24.
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