CHEM 14A Chapter Notes - Chapter 2B.2: Benzene, Lewis Structure
18 Nov 2020
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Some molecules are not represented adequately by a single lewis structure. These three lewis structures differ only in the position of the double bond. All are valid structures and they have the same energy. Resonance hybrid: a merging of structures; a molecule does not flicker between different structures. Electrons that are shown in different positions in a set of resonance structures are said to be delocalized. Delocalization: a shared electron pair is distributed over several pairs of atoms and cannot be identified with just one pair of atoms. The three resonance structures above do no exist as actual molecules; they are simply a way of showing that the electrons are spread across the molecule. Resonance also lowers the energy below that of any single contributing structure and helps to stabilize the molecule. In each contributing structure, the nuclei are in the same positions; only the locations of lone pairs and bonding pairs are changed.
