Resonance: Equivalent Lewis Structures for the

Same Molecule

• When writing Lewis structures for some molecules, such as SO2, we can write more than one good Lewis structure.
• Begin with the skeletal structure:

O S O

• Sum the valence electrons.

(# valence e− in S) + 2(# valance e− in O)

6 e− + 2(6 e− ) = 18 e−