Chromium(II) oxide

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Chromium(II) oxide
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IUPAC name
chromium(II) oxide
PubChem CID
Molar mass 67.996 g/mol
Melting point 300 °C (572 °F; 573 K) (decomposes)
cubic, cF8
Fm3m, No. 225
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chromium(II) oxide (CrO) is an inorganic compound composed of chromium and oxygen. [1] It is a black powder that crystallises in the rock salt structure. [2] Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide:

H3PO2 + 2 Cr2O3 → 4 CrO + H3PO4

It is readily oxidized by the atmosphere. CrO is basic, while CrO3 is acidic, and Cr2O3 is amphoteric. [3]

CrO occurs in the spectra of luminous red novae, which occur when two stars collide. It is not known why red novae are the only objects that feature this molecule; one possible explanation is an as-yet-unknown nucleosynthesis process. [4]

See also

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An oxyanion, or oxoanion, is an ion with the generic formula A
. Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound H
. The structures of condensed oxyanions can be rationalized in terms of AOn polyhedral units with sharing of corners or edges between polyhedra. The oxyanions adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are important in biology.

<span class="mw-page-title-main">Chromate and dichromate</span> Chromium(VI) anions

Chromate salts contain the chromate anion, CrO2−
. Dichromate salts contain the dichromate anion, Cr
. They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible.

An acidic oxide is an oxide that either produces an acidic solution upon addition to water, or acts as an acceptor of hydroxide ions effectively functioning as a Lewis acid. Acidic oxides will typically have a low pKa and may be inorganic or organic. A commonly encountered acidic oxide, carbon dioxide produces an acidic solution when dissolved.

<span class="mw-page-title-main">Chromium(III) chloride</span> Chemical compound

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Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions, bright orange when wet and which dissolves in water concomitant with hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser and a carcinogen.

<span class="mw-page-title-main">Chromium(III) oxide</span> Chemical compound

Chromium(III) oxide is an inorganic compound with the formula Cr
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<span class="mw-page-title-main">Chromium(II) acetate</span> Chemical compound

Chromium(II) acetate hydrate, also known as chromous acetate, is the coordination compound with the formula Cr2(CH3CO2)4(H2O)2. This formula is commonly abbreviated Cr2(OAc)4(H2O)2. This red-coloured compound features a quadruple bond. The preparation of chromous acetate once was a standard test of the synthetic skills of students due to its sensitivity to air and the dramatic colour changes that accompany its oxidation. It exists as the dihydrate and the anhydrous forms.

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Chromium(III) fluoride is the name for the inorganic compounds with the chemical formula CrF3 as well as several related hydrates. The compound CrF3 is a green crystalline solid that is insoluble in common solvents, but the coloured hydrates [Cr(H2O)6]F3 and [Cr(H2O)6]F3•3H2O are soluble in water. The trihydrate is green, and the hexahydrate is violet. The anhydrous form sublimes at 1100–1200 °C.

<span class="mw-page-title-main">Chromium(II) chloride</span> Chemical compound

Chromium(II) chloride describes inorganic compounds with the formula CrCl2(H2O)n. The anhydrous solid is white when pure, however commercial samples are often grey or green; it is hygroscopic and readily dissolves in water to give bright blue air-sensitive solutions of the tetrahydrate Cr(H2O)4Cl2. Chromium(II) chloride has no commercial uses but is used on a laboratory-scale for the synthesis of other chromium complexes.

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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.

<span class="mw-page-title-main">Iron(III) acetate</span> Chemical compound

Ferric acetate is the acetate salt of the coordination complex [Fe3O(OAc)6(H2O)3]+ (OAc is CH3CO2). Commonly the salt is known as "basic iron acetate". The formation of the red-brown complex was once used as a test for ferric ions.

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Nickel(II) chromate (NiCrO4) is an acid-soluble compound, red-brown in color, with high tolerances for heat. It and the ions that compose it have been linked to tumor formation and gene mutation, particularly to wildlife.

<span class="mw-page-title-main">Jones oxidation</span>

The Jones oxidation is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones. The reaction was an early method for the oxidation of alcohols. Its use has subsided because milder, more selective reagents have been developed, e.g. Collins reagent.

<span class="mw-page-title-main">Chromyl fluoride</span> Chemical compound

Chromyl fluoride is an inorganic compound with the formula CrO2F2. It is a violet-red colored crystalline solid that melts to an orange-red liquid.

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Chromium(II) sulfate refers to inorganic compounds with the chemical formula CrSO4·n H2O. Several closely related hydrated salts are known. The pentahydrate is a blue solid that dissolves readily in water. Solutions of chromium(II) are easily oxidized by air to Cr(III) species. Solutions of Cr(II) are used as specialized reducing agents of value in organic synthesis.

Chromium pentafluoride is the inorganic compound with the chemical formula CrF5. It is a red volatile solid that melts at 34 °C. It is the highest known chromium fluoride, since the hypothetical chromium hexafluoride has not yet been synthesized.

<span class="mw-page-title-main">Chromium(III) phosphate</span> Chemical compound

Chromium(III) phosphate describes inorganic compounds with the chemical formula CrPO4.(H2O)n, where n = 0, 4, or 6. All are deeply colored solids. Anhydrous CrPO4 is green. The hexahydrate CrPO4•6H2O is violet.

<span class="mw-page-title-main">Chromium(III) perchlorate</span> Chemical compound

Chromium(III) perchlorate is an inorganic compound with the chemical formula Cr(ClO4)3. It's hexahydrate Cr(ClO4)3·6H2O is a cyan solid that dissolves in water.


  1. Satish. Anand, Raj. Kumar (1989), Dictionary of Inorganic Chemistry, Anmol Publications, ISBN   978-81-7041-236-6
  2. Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN   0-12-352651-5
  3. Chemistry 7th edition, by Raymond Chang page 645 (problem 15.100)
  4. Kamiński, T.; Mason, E.; Tylenda, R.; Schmidt, M. R. (2015). "Post-outburst spectra of a stellar-merger remnant of V1309 Scorpii: From a twin of V838 Monocerotis to a clone of V4332 Sagittarii". Astronomy & Astrophysics. 580: A34. arXiv: 1504.03421 . Bibcode:2015A&A...580A..34K. doi:10.1051/0004-6361/201526212. S2CID   118566357.