<Dl> <Dd> The unit cell of rutile . Ti (IV) centers are grey; oxide centers are red . Notice that oxide forms three bonds to titanium and titanium forms six bonds to oxide . </Dd> </Dl> <Dd> The unit cell of rutile . Ti (IV) centers are grey; oxide centers are red . Notice that oxide forms three bonds to titanium and titanium forms six bonds to oxide . </Dd> <P> An oxide / ˈɒksaɪd / is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula . "Oxide" itself is the dianion of oxygen, an O atom . Metal oxides thus typically contain an anion of oxygen in the oxidation state of − 2 . Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water . Hydrocarbon combustion affords the two principal carbon oxides: carbon monoxide and carbon dioxide . Even materials considered pure elements often develop an oxide coating . For example, aluminium foil develops a thin skin of Al O (called a passivation layer) that protects the foil from further corrosion . Individual elements can often form multiple oxides, each containing different amounts of the element and oxygen . In some cases these are distinguished by specifying the number of atoms as in carbon monoxide and carbon dioxide, and in other cases by specifying the element's oxidation number, as in iron (II) oxide and iron (III) oxide . Certain elements can form many different oxides, such as those of nitrogen . </P> <P> Due to its electronegativity, oxygen forms stable chemical bonds with almost all elements to give the corresponding oxides . Noble metals (such as gold or platinum) are prized because they resist direct chemical combination with oxygen, and substances like gold (III) oxide must be generated by indirect routes . </P>

What must be present for a compound to be referred to as an oxide