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What is the structure of SO2? I have seen two different ways the Lewis Structure is written: Single and Double Two double bonds

The formal charges of the SO2 with the single bond and a double bond is larger than the SO2 with two double bonds. So I would assume that the one with two double bonds is the correct structure. But chemistry books I have looked at (Zumdahl Edition 5 and 7) says that it is the opposite.

Which is the correct Lewis Structure?

Hawkeye
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The Lewis structure most closely resembling reality consists of two resonance structures: the first one posted in the question and its mirror image. The reason is that the octet rule is observed this way (no hybridization of d-orbitals for main group chemistry necessary or possible) as well as the symmetry of the molecule: the two bonds are identical.

TAR86
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  • I had the notion that sulfur had expanded valence electrons. So why wouldn't sulfur be able to use them and make the formal charges get to 0 for all three atoms? Also, how does the molecule have symmetry? The bonds aren't identical, one is a single bond and the other is a double bond. – Hawkeye Dec 08 '17 at 19:39
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    The identical bonds are a physically observable reality. Expanded valence electrons are an outdated concept refuted by modern quantum chemistry. – TAR86 Dec 08 '17 at 20:05
  • How does sulfur make a molecule such as Sulfur Hexafluoride in modern quantum chemistry, since expanded valence electrons are outdated? – Hawkeye Dec 08 '17 at 21:00
  • @Hawkeye check out molecular orbital theory. You can easily hold sulfur hexafluoride together without using "outer $d$ orbitals". – Oscar Lanzi Dec 08 '17 at 23:41