CHEM 14A Chapter Notes - Chapter 2D.1-2: Lewis Structure, Chemical Polarity, Bromine
18 Nov 2020
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A single lewis structure is only the initial step in formulating a description of a covalently bonded molecule. This can be improved by using resonance to blend together alternative molecule. In this case, the ionic structures make only a small contribution to the resonance hybrid. The two ionic structures have the same energy and make equal contributions to the hybrid. The average charge on each atom is zero. The resonance has unequal contributions from the two ionic structures. The chlorine atom has a greater attraction for electrons than does the hydrogen atom. The structure with the negative charge on the cl atom makes a bigger contribution than the other. As a result, there is a small net negative charge on the cl atom and a small net positive charge on the h atom. Partial charges: the net changes, the average outcome of the resonance, on the atoms in hcl.
