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Double Bonds

Posted: Mon Nov 04, 2019 9:34 pm
by Ellis Song 4I
How do you know which atoms to form a double bond with when drawing a lewis structure? For example, why does the double bond form between O and N instead of F and N in the molecule ONF

Re: Double Bonds

Posted: Mon Nov 04, 2019 9:42 pm
by pmokh14B
Using formal charges can help with this. A double bonded O with two lone pairs would have a formal charge of zero, whereas if it had a single bond with three unpaired e- the formal charge would be -1, which is unfavorable. The same thing goes for F.

Re: Double Bonds

Posted: Mon Nov 04, 2019 9:42 pm
by 905416023
You have to focus on the formal charge to decide when to place a double bond. Whichever structure results in the lowest formal charge is the one you want.

Re: Double Bonds

Posted: Mon Nov 04, 2019 9:43 pm
by Sophia Shaka 3L
You need to look at electronegativity. You can see which atoms are more electronegative based on the periodic trend. Calculating formal charge will also be helpful in determining where to put double bonds, as highly electronegative atoms are able to have a negative formal charge.