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Resonance and Bond Length

Posted: Sun Oct 23, 2016 12:30 am
by Nicole Gamboa 2M
Hi All,
I was going over my notes on resonance and bond length and I found myself pretty confused on how resonance affects the length of a bond and why the bond in a structure with resonance is experimentally observed as the average between two bond lengths rather than a single shorter or longer bond?

Re: Resonance and Bond Length

Posted: Sun Oct 23, 2016 1:47 pm
by Joseph Nguyen 3L
You see, the Lewis structure is an imperfect model for "representing" bonds. For a resonance structure, the double bonds can be in different locations, and let's say a double bond is 1A in length but a single bond is 2A because it is larger. But when you do the experiment, you find that all of the bonds have a length of 1.5. Resonance structures are only meant to show that those lengths and bonds BLEND together as an average because electrons are delocalized, meaning the electrons don't stay in any ONE lone pair. Therefore the electrons are distributed evenly throughout the molecule, creating resonance.