The structural formula of carbon monoxide is given as CO. This is because 10 valence electrons are available, so a triple bond is formed. Of six shared electrons, oxygen contributes four and carbon contributes two, causing the formation of a small dipole, creating a weakly polar molecule.
Carbon monoxide is created when carbon is burned in an environment with a limited oxygen supply. In this situation, the combustion of carbon remains incomplete, resulting in only half the amount of oxygen combining with the carbon. When oxygen is abundant, complete combustion occurs, and carbon dioxide (CO2) is the result. If very little air is present, pure carbon is created.