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Resonance

Posted: Sun Nov 24, 2019 11:59 pm
by Diana A 2L
When writing a resonance structure, do we do the resonance of the Lewis structure with the best balance of formal charges, or are the structures with imbalanced formal charges that are still correct also count as resonance?

Re: Resonance

Posted: Mon Nov 25, 2019 12:03 am
by Angus Wu_4G
Only structures with the best balance of formal charges count as resonance. Keep in mind that you want the most electronegative element in your molecule to carry the negative formal charge, and the least electronegative element to carry the positive formal charge. It is ideal if all the formal charges can be zero though.

Re: Resonance

Posted: Mon Nov 25, 2019 12:05 am
by Laura WM 3I
It it better to have 2 formal charges of -1 or 1 formal charge of -2?

Re: Resonance

Posted: Mon Nov 25, 2019 11:24 am
by ZainAlrawi_1J
2 charges of 1 or -1 is usually preferable.

Re: Resonance

Posted: Mon Nov 25, 2019 1:06 pm
by Natalie Benitez 1E
Laura WM 3I wrote:It it better to have 2 formal charges of -1 or 1 formal charge of -2?

This depends on the element itself. If one element is more electronegative compared to the other then you should place the negative charge on the element with the higher electronegativity.

Re: Resonance

Posted: Mon Nov 25, 2019 5:44 pm
by Anna Heckler 2C
When drawing resonance structures, you still only want the lewis structures with the most "well balanced" formal charges. Note that the negative charge should always go on the most electronegative atom.