Molecular Compounds

Not all compounds are formed from ions. However, it is often helpful to calculate oxidation numbers for these compounds. It allows us to keep track of the movement of electrons in many reactions (particularly in oxidation/reduction reactions such as rusting).

For example, in carbon monoxide, CO, we assign the oxygen a "-2" oxidation number (we'll learn where this number came from shortly). This means that the carbon must have a "+2" oxidation number so that the total adds up to zero.



The carbon and oxygen atoms do not really have charges. They are not ions and are held together by covalent bonds. However, we assign oxidation numbers and pretend they have charges as a form of "electron bookkeeping." Next we'll learn the rules for assigning oxidation numbers.