A monoxide is any oxide containing just one atom of oxygen in the molecule. For example, Potassium oxide (K₂O), has only one atom of oxygen, and is thus a monoxide. Water (H₂O) is also a monoxide; see dihydrogen monoxide hoax. A well known monoxide is carbon monoxide (CO); see carbon monoxide poisoning.most of the members in periodic table forms oxides when oxidized.there are mainly two types of oxides.monoxides and dioxides.monoxides(generally MO)like silicon monoxide(SiO) only exists at high temperature.among monoxides,CO is neutral.GeO is distinctly acidic whereas SnO and PbO are amphoteric.

Le protoxyde d'une substance chimique est le composé le moins oxygéné parmi tous ceux qui peuvent être formés en se combinant avec l'oxygène.