The gaseous compound carbon monoxide, or CO, is formed when one atom of carbon chemically combines with one atom of oxygen during incomplete combustion. When complete combustion occurs, carbon dioxide, CO2, is created where one atom of carbon reacts with two atoms of oxygen.
The chemical element carbon exists in nature in several different physical forms called allotropes. Diamond and graphite are the two crystalline structures of carbon while charcoal, carbon black and coke are some of the element's noncrystalline shapes. One of the characteristics of carbon is the formation of strong double and triple chemical bonds with several nonmetallic elements, such as nitrogen, phosphorus, sulfur and oxygen.
A binary compound called an oxide is produced when an element chemically reacts with oxygen in a process known as oxidation. When the oxidation process releases heat, light and creates a new product, it is referred to as a combustion reaction.
CO2 is a colorless, odorless gas, which is the primary product of complete combustion. It is produced when carbon-rich compounds, such as charcoal and coke, are burned where there is an abundant supply of air, specifically oxygen. Incomplete combustion occurs when carbon is burned where there is an insufficient amount of air. CO is also a colorless, odorless gas and is the main product of incomplete combustion. Exposure to high levels of CO is considered dangerous and is sometimes fatal.