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Oxyanion

    An '''oxyanion''' or '''oxoanion''' is a negatively charged polyatomic ion that contains oxide Oxyanions can be viewed as the conjugate base of a corresponding oxyacid although both components are not necessarily stable Probably the best known oxyanion is DNA The most extensive family of oxyanions are the polyoxometallate|polyoxomolybdates
    Some elements Q, (Q = metals and nonmetals) form several oxyanions QOxn- with different numbers of oxygen atoms x, or different charges n. These oxyanions and their conjugate oxyacids are named according to the oxidation state of the non-oxygen atom for example the four oxyanions of chlorine:

    Oxidation state +1 +3 +5 +7
    oxanion name hypochlorite chlorite chlorate perchlorate
    formula 2}}3}}4}}
    structure ion
    Conjugate acid Hypochlorous acid Chlorous acid Chloric acid Perchloric acid
    structure

    For other oxyanions the oxidation states may be different from these but the order of the prefixes and suffixes remains the same

    Well known oxyanions

    • With terminal oxide groups:
      • borate
      • carbonate
      • nitrate nitrite hyponitrite
      • aluminate
      • silicate
      • phosphate phosphite hypophosphite
      • persulfate sulfate sulfite hyposulfite
      • perchlorate chlorate chlorite hypochlorite
      • chromate
      • permanganate manganate
    • With both bridging and terminal oxide groups:
      • peroxydisulfate
      • dichromate
      • pyrophosphate
      • polyoxometalates such as phosphomolybdate and phospohtungstate

    Oxyanions have some very important environmental roles We can mention the case of prvalence of arsenic species in the arsenic affected areas in the form of oxyanions Surface water usually exhibit oxidizing conditions and under such condition arsenic species tend to prevail in pentavalent arsenic form mainly in its oxyanionic forms H2AsO4- and HAsO42-