Formal Charge and Lewis Structures

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MorganYun1H
Posts: 59
Joined: Thu Jul 13, 2017 3:00 am

Formal Charge and Lewis Structures

Postby MorganYun1H » Mon Oct 30, 2017 5:28 pm

If we draw a Lewis structure and the formal charge isn't zero for multiple different formations, do we draw all of the possible arrangements as a resonance? For example, 3.35b has BrO^- but when you calculate the formal charge with a single bond, O has a -1 charge. When there is a double bond between O and Br, Br has a +1 charge. So if I'm writing the lewis structure, do I write both with double headed angle in between?

Ethan-Van To Dis2L
Posts: 50
Joined: Fri Sep 29, 2017 7:05 am

Re: Formal Charge and Lewis Structures

Postby Ethan-Van To Dis2L » Mon Oct 30, 2017 10:19 pm

There part where you mentioned the double bond and the Br with a +1 charge is actually incorrect. If you form a double bond by taking a pair of electrons from Br, that would mean O would have 10 electrons which can't happen since it has no d-orbital. In this case I think we consider Br the central atom and as in most molecules it is best to have the central atom with a formal charge of 0. If you made a double bond by taking away a lone pair from O, Br would have a charge of -1.

Hammad Khan 2B
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Joined: Fri Sep 29, 2017 7:07 am
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Re: Formal Charge and Lewis Structures

Postby Hammad Khan 2B » Wed Nov 01, 2017 9:51 am

What I understand is that the central atom should try and achieve FC=0 and the other atoms should also try to approach this value if possible. But if there are multiple arrangements where the central atom has FC=0 and the other atoms just interchange charge, then we can show resonance between the structures as each one is stable enough to be used as the correct configuration.


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