Carbon monoxide does not form an ionic compound. It is a covalent compound, meaning the atoms share electrons rather than transferring them to form ions.

Here's why:

* Carbon and oxygen have similar electronegativity: Electronegativity is the ability of an atom to attract electrons. The difference in electronegativity between carbon and oxygen is not large enough to create a full transfer of electrons, which is necessary for ionic bonding.

* Carbon monoxide is a gas: Ionic compounds are typically solids at room temperature, while covalent compounds can be solids, liquids, or gases.

The chemical formula for carbon monoxide is CO.