Ions can be cations or anions, with oxygen often being part of oxyanions or oxications. Oxyanions can be derived from acids and can consist of nonmetals or metals. Some, like dichromate and permanganate, act as oxidizers. The formation and stability of oxyanions depend on factors like electron configuration and symmetry. Fluorine is an exception, forming only one unstable oxyacid. Sulfate is one of the most stable oxyanions due to its resonance structures.
An ion is a non-neutral atom or set of atoms functioning as a unit. If the ion has an electron deficit, it is a “cation”, but if it has an electron surplus, it is an “anion”. When oxygen is part of the cation, it is an oxication, such as uranyl (UO2)+2. Alternatively, if oxygen atoms are part of the anion, it is an oxyanion, as in nitrate (-NO3)-1. Rarely, both ions are oxygenated, having both an oxication and an oxyanion. One of the best known examples is uranyl nitrate (UO2)(NO3)2.
There are numerous varieties of oxyanion. Among these are sulfate (SO4)-2, acetate (CH3COO)-1 and tellurite (TeO3)-2. Other types of oxyanion include perchlorate (ClO4)-1, phosphate (PO4)-3 and nitrate (NO3)-1.
An oxyanion can usually be written as the corresponding acid from which it is derived. In this case we have sulfuric, acetic, tellurous, perchloric and nitric acids. The removal of water from these acids gives the anhydrides: sulfur dioxide, acetic anhydride, tellurium dioxide, chlorine heptoxide, phosphorus pentoxide and nitrogen dioxide. In particular, inorganic oxyanions often consist of oxygen plus a nonmetal, such as sulfur, nitrogen, or phosphorus; however, they can also consist of a metal and oxygen.
Two species of metal-containing oxyanions are dichromate and permanganate. Potassium dichromate (K2Cr2O7) is often used in organic chemical reactions as an oxidizing agent; potassium permanganate (KMnO4) is an even more powerful oxidizer. When combined with sulfuric acid, it produces the explosive substance permanganic acid anhydride, or manganese heptoxide (Mn2O7), according to the reaction equation 2 KMnO4 + H2SO4 → K2SO4 + Mn2O7 + H2O. Contrary to the nature of permanganate, some oxyanion compounds do not act as oxidizers at all. This is due to a number of factors, including electronegativity, ion size, electron configuration, and resonance stabilization.
The electron configuration that allows for the formation of oxyanions requires the presence of expandable electron d-shell orbitals, which allow for higher atomic valence levels. Although three of the halogens, namely chlorine, bromine and iodine, have such envelopes and can also form highly oxygenated anions, fluorine does not. It can form only one oxygenated acid, hypofluorine acid, and that is so unstable that it explodes easily. An additional factor that contributes to both the formation and stability of an oxyanion is the symmetry of the ion resonance. One of the most stable oxyanion structures, sulfate can be drawn as one of six possible equivalent resonance structures, effectively spreading the negative charge over a large external surface area.
Protect your devices with Threat Protection by NordVPN
