Question

Please draw 2 Lewis structures of H₂SO₃. The first Lewis structure should follow the octet rule while the second structure does not follow the octet rule. Please use formal charge on both structures and identify which of the two is the more stable Lewis structure. If the one that follows the octet rule is more stable, please draw a smiley face. If the structure which does not follow the octet rule is more stable, please specify to which exception of the octet rule this structure belongs.

Answer 1

The Lewis structures of are shown below.

H2SO3

:7: Hö-s-OH :O: HÖ-5-OH

Octet is complete for structure I. Each O atom and S atom has 8 electrons in valence shell. Each H atom has 2 electrons.

Octet is incomplete for structure II. Each O atom has 8 electrons in valence shell. Each H atom has 2 electrons. But S atom has 10 valence electrons. It represents expanded octet.

The formal charges are shown in red numbers.

0:1 0.0 0.0 HO-S-OH :O: 0. 1 0. HO-S-OH O Ö " less stable more stable

Structure II is more stable than structure I. This is because there is no charge separation structure II. But there is charge separation in structure I. Those resonance structures which have minimum (or no) charge separation are more stable than those structures with charge separation.