Use the remaining electrons to give lone pairs to the terminal atoms in order to satisfy the octet rule. Use any remaining electrons to give the central atom one or more lone pairs. Draw any resonance forms. True structure is the average of these forms. Resonance forms show the delocalization of charge .
Formal charge assumes equal sharing of electrons.
Oxidation number assumes transfer of electrons to the more electronegative atom. CO 2 Electron density isosurfaces of CO 2 . Electron density contour plot for CO 2 . Charges for atoms in CO 2 . The octet rule is always obeyed for C, N, O, F .