Binary compounds formed between elements and oxygen. Oxides of nonmetals are covalent compounds having simple molecules (e.g. CO, CO2, SO2) or giant molecular lattices (e.g. SiO2). They are typically acidic or neutral. Oxides of metals are ionic, containing the O2− ion. They are generally basic or amphoteric. Various other types of ionic oxide exist (see ozonides; peroxides; superoxides).