higheroxide

In inorganic chemistry, a higher oxide of an element is an oxide in which the element is in a higher oxidation state than in another oxide of the same element. The term is relative rather than a formal class, and it is often used to compare the series of oxides formed by elements as their oxidation state changes. Commonly cited pairs include nitrogen, sulfur, phosphorus, chlorine, and manganese.

Examples include nitrogen: N2O (nitrous oxide, with nitrogen formally in the +1 state) and N2O5 (dinitrogen pentoxide, +5). Sulfur forms SO2 (sulfur in +4) and SO3 ( +6). Phosphorus has P4O6 (phosphorus(III)) and P4O10 (phosphorus(V)). Chlorine forms Cl2O (chlorine(I)) and Cl2O7 (chlorine(VII)). Manganese provides MnO (Mn(II)) and Mn2O7 (Mn(VII)).

Higher oxides are often more oxidizing and less stable than their lower counterparts. They may exist as discrete molecular species or as part of condensed phases. Hydration or acid formation is common: for example, N2O5 hydrolyzes to HNO3, and Cl2O7 forms HClO4 upon contact with water. Their synthesis typically requires strong oxidizing conditions.

Note that "higher oxide" is not a formal IUPAC category but a descriptive label used to discuss oxides across oxidation states. The related concepts of lower oxides, peroxides, and superoxides provide additional context for oxide chemistry.