CO, also known as carbon monoxide, is a compound. It is composed of two different elements: carbon (C) and oxygen (O). In CO, one atom of carbon is chemically bonded to one atom of oxygen. This combination of elements in a fixed ratio is what defines a compound.
Carbon monoxide is a colorless, odorless gas that is produced by the incomplete combustion of carbon-containing materials. It is important to note that while both carbon and oxygen are elements on their own, when they combine in this specific way, they form a compound with unique properties different from those of the individual elements.