CHEM101: General Chemistry I

Sometimes we can draw more than one Lewis structure for a given molecule or polyatomic ion that are not equivalent. In this case, we use a concept called formal charge to determine, which Lewis structure is best. Formal charge is not actually a charge; rather, it is just a system to keep track of electrons in a given Lewis structure.

Watch these two videos, which teach you the rules for assigning formal charge to atoms in a Lewis structure, and show examples of using formal charge to determine the best possible Lewis structure for a given molecule.