Lewis Structure of SO2

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Ishan Saha 1L
Posts: 60
Joined: Fri Sep 29, 2017 7:03 am

Lewis Structure of SO2

Postby Ishan Saha 1L » Thu Nov 09, 2017 2:35 pm

Hi! I was just wondering if the Lewis structure of SO2, sulfur dioxide, has two double bonds between S-O with a lone pair on Sulfur (making expanded octet), OR if it has one single bond and one double bond, with one lone pair on Sulfur (allowing it to stay within the octet rule). The first option allows all formal charges to equal zero, but I'm reading mixed answers online that the correct structure is the latter option, so I don't know what is correct.

Leon Popa
Posts: 18
Joined: Fri Sep 29, 2017 7:04 am

Re: Lewis Structure of SO2

Postby Leon Popa » Thu Nov 09, 2017 2:54 pm

Hi Ishan,
From what I understand, all of those lewis structures are valid. They're essentially resonance structures, but the first structure you mentioned, with two double bonds, is the preferred one. This is because all formal charges are zero. In the structure with one single bond and one double bond, the Sulfur has a +1 formal charge and the oxygen with a single bonds has a -1 formal charge. Overall, the formal charge of the molecule is zero, but the lack of balance in formal charges on either side of the sulfur makes this resonance structure less stable. So the first version you mentioned, I believe, is the correct one.

Hope that helps.
- Leon

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