Why Resonance for SO2?

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Natalie Noble 1G
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Why Resonance for SO2?

Postby Natalie Noble 1G » Fri May 25, 2018 3:45 pm

In a UA session there was a problem where it asked for three resonance structures for SO2. But when I made the Lewis Structure for SO2 it's stablest form was
the S with double bonds to each O and one lone pair of electrons and
the two O had two sets of lone pairs
With this the formal charge was all zero, and there wasn't any resonance as both the oxygen had double bonds, so I'm confused how I'm supposed to get 2 other resonant structures.

Fiona Grant 1I
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Joined: Fri Apr 06, 2018 11:03 am

Re: Why Resonance for SO2?

Postby Fiona Grant 1I » Fri May 25, 2018 3:46 pm

You are correct that the structure with 2 double bonds is the most stable structure. However, since the question specifically asks for three resonance structures, you should also include the two resonance structures that have 1 single bond and 1 double bond between the S and each O, even though they aren’t the most stable structures.

If the question had asked for you to draw the most stable Lewis structure, you would only need to draw the one structure. It’s because the question asks for three resonance structures that you need to draw three structures in order to fully complete the problem.

Beverly Shih 1K
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Re: Why Resonance for SO2?

Postby Beverly Shih 1K » Fri May 25, 2018 10:24 pm

I thought that for structures to have resonance, they had to have the same energy level. Does this mean resonant structures can have different levels of energy?

Tiffany Tufenkjian 1E
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Re: Why Resonance for SO2?

Postby Tiffany Tufenkjian 1E » Sat May 26, 2018 2:59 pm

Screen Shot 2018-05-26 at 2.57.17 PM.png

Resonance structures should have the same energy levels.

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