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Chromium compounds are compounds containing the element chromium (Cr). Chromium is a member of group 6 of the transition metals. The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist. [3] [4]
Compounds of chromium(V) are rather rare; the oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate. The only binary compound is the volatile chromium(V) fluoride (CrF 5). This red solid has a melting point of 30 °C and a boiling point of 117 °C.
Chromium is a very common naturally occurring element. It is the 21st most abundant element in the Earth's crust with an average concentration of 100 ppm. The most common oxidation states for chromium are zero, trivalent, and hexavalent states. Most naturally occurring chromium is in the hexavalent state. [20]
The oxidation states are also maintained in articles of the elements (of course), and systematically in the table {{Infobox element/symbol-to-oxidation-state}} See also [ edit ]
Oxidation states are typically represented by integers which may be positive, zero, or negative. In some cases, the average oxidation state of an element is a fraction, such as 8 / 3 for iron in magnetite Fe 3 O 4 . The highest known oxidation state is reported to be +9, displayed by iridium in the tetroxoiridium(IX) cation (IrO + 4). [1]
Because of the very high melting point of chromium, chromium thermite casting is impractical. Heating with chlorine and carbon yields chromium(III) chloride and carbon monoxide: Cr 2 O 3 + 3 Cl 2 + 3 C → 2 CrCl 3 + 3 CO. Chromates can be formed by the oxidation of chromium(III) oxide and another oxide in a basic environment: 2 Cr 2 O 3 + 4 MO ...
The chromium cycle is the ... Chromium has two common oxidation states ... Hexavalent chromium is reduced to trivalent chromium in oxygen minimum zones or at the ...
A chromate ester is a chemical structure that contains a chromium atom (symbol Cr) in a +6 oxidation state that is connected via an oxygen (O) linkage to a carbon (C) atom. The Cr itself is in its chromate form, with several oxygens attached, and the Cr–O–C attachment makes this chemical group structurally similar to other ester functional groups.