Resonance

Resonance structures are two forms of a molecule where the chemical connectivity is the same but the electrons are distributed differently around the structure. Resonance occurs when electrons can flow through neighboring pi systems. An important example of resonance is found in the bonding of benzene, a planar six-membered ring with alternating double and single bonds (three of each). Two distinct pictures can be drawn, and the true structure of the molecule is a mixture of the two resonance structures. Having multiple valid resonance structures makes a molecule more energetically stable. Resonance helps to explain structure and reactivity of organic molecules.