Does a resonance structure have more than one Lewis formula?

1 Answer
Truong-Son N.
May 8, 2018

Each resonance structure only corresponds to one chemical formula... but a single resonance structure has a fixed structure by definition of it being a snapshot of a molecular electronic configuration.

The one chemical formula can have more than one resonance structure, and typically, a stable molecule will have more than one resonance structure.

Take nitrate anion for example... #"NO"_3^(-)#:

http://i.stack.imgur.com/

Each resonance structure corresponds to only one chemical structure, and that's the one you see on the page. In this case we just have three degenerate structures; if you rotate the first one #120^@# clockwise you get the second one, and so on.

But that is no coincidence. This rotational symmetry is what then sensibly gives the resonance hybrid structure, which has 3-fold rotational symmetry axis through the page:

https://upload.wikimedia.org/

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