Chromium is the 21st or 22nd most abundant element in the Earth's crust.The coated is metal is usually called chrome. Chromium in air is passivated by oxygen, forming a protective layer that is essentially a spinel that is a few atoms thick.Chromium is used to prepare pigments (including yellow, red, and green), to color glass green, to color rubies red and emeralds green, in some tanning processes, as a decorative and protective metal coating, and as a catalyst.The most stable isotope is chromium-50, which has a half-life of over 1.8×10 17 years. Nineteen radioisotopes have been characterized. Chromium-52 is the most abundant isotope, accounting for 83.789% of its natural abundance. Chromium occurs naturally as a mix of three stable isotopes: Cr-52, Cr-53, and Cr-54.The +1, +4, and +5 oxidation states also occur, although they are less common. Hexavalent chromium and its compounds are extremely toxic and also carcinogenic. Trace amounts of trivalent chromium are needed for lipid and sugar metabolism.Chromium becomes paramagnetic above 38 degrees Celsius. The element's magnetic properties are among its most notable characteristics. Chromium is the only element that shows antiferromagnetic ordering in its solid state at and below room temperature.Stainless steel is hard and resists corrosion due to the addition of chromium.Like many transition metals, it has a high melting point (1,907 degrees C, 3,465 F) and a high boiling point (2,671 degrees C, 4,840 F). Chromium is a hard, lustrous, steel-gray metal. Chromium may be highly polished.It is the first element in group 6 on the periodic table, with an atomic weight of 51.996 and a density of 7.19 grams per cubic centimeter.
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