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The uranyl ion is the dipositive cation [UO2]2+, which forms salts with acids. In this ion, uranium is in its +6 oxidation state. The other common oxidation state of uranium is uranium(IV), called uranous. The uranyl ion is the most common species encountered in the aqueous chemistry of uranium. Solid uranyl compounds are often colored red, yellow, orange or green. Like all uranium compounds, uranyl compounds are toxic. The toxicity of soluble uranyl salts is higher due to their faster incorporation into tissues.
Additional recommended knowledge
Examples of uranyl compounds include:
Such minerals occur in oxidised portions of uranium ore deposits. Common uranyl minerals include tyuyamunite (Ca(UO2)2V2O8·8H2O), autunite (Ca(UO2)2(PO4)2·8-12H2O), torbernite (Cu(UO2)2 (PO4)·8-12H2O) and uranophane (H3O)2Ca (UO2)2(SiO4)·3H2O) (Hutchinson and Blackwell, 1984). Uranyl minerals, which contain uranium(VI) can help show the genesis of uranium deposits and the water-rock interactions that occur in uranium-rich mineral seams.
Uranium chemistry has traditionally revolved around the aqueous chemistry of the uranyl ion, and related molecular species. One important use of this chemistry is for preparation of uranium dioxide ceramic pellets that are used as the fuel in light water nuclear reactors. Often the fuel materials start to break down chemically before the uranium is completely spent, and this too is an active area of investigation, as many of the corrosion products are of the uranyl group.
The geometry of the uranyl ion has been the subject of much debate. The close approach of two oxygen atoms to uranium, with each linear O-U-O bond from 1.7 to 1.9 Å, prevents the close approach of a third or more. d-p and f-p bonding have been suggested to explain the short U-O bonds.
Health and environmental issues
Uranyl nitrate is an oxidizing and highly toxic compound and should not be ingested; it causes severe renal insufficiency and acute tubular necrosis and is a lymphocyte mitogen.
Target organs include the kidneys, liver, lungs and brain. Uranyl ion accumulation in tissues including gonocytes produces congenital disorders, and in white blood cells causes immune system damage. Uranyl compounds are also neurotoxins.
Combustion of uranium
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Uranyl". A list of authors is available in Wikipedia.|