SO2 and SO3 bond length

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Isabel Nakoud 4D
Posts: 101
Joined: Thu Sep 27, 2018 11:27 pm

SO2 and SO3 bond length

Postby Isabel Nakoud 4D » Tue Nov 27, 2018 2:46 pm

When comparing the bond lengths of SO2 and SO3..
Both structures are made up entirely of double bonds... however, SO2 has lone pairs on the Sulfur and SO3 does not, so would it be correct to assume that SO2 had slightly longer bonds than SO3? (I am assuming that the bonds in SO2 would be longer because of the electron repulsion from the lone pairs)

MaanasO 1A
Posts: 60
Joined: Thu Sep 27, 2018 11:26 pm

Re: SO2 and SO3 bond length

Postby MaanasO 1A » Tue Nov 27, 2018 5:14 pm

Hi Isabel!

The bond lengths actually won't change based on the electron lone pairs. The bond ANGLES, however, will be slightly different due to the repulsion of lone pair electrons.

Hope that helps!

Dana Wilks 3I
Posts: 30
Joined: Thu Sep 27, 2018 11:23 pm

Re: SO2 and SO3 bond length

Postby Dana Wilks 3I » Tue Nov 27, 2018 5:33 pm

As stated above, the bond angles will be different for the two compounds.

SO2 has two oxygen atoms bonded to the central sulfur atom. Because the sulfur atom does not adhere to the octet rule, it also has an additional lone pair, which repels the two oxygen atoms, giving it an electron arrangement of trigonal planar and a molecular shape of bent/angular.

SO3, on the other hand, has no lone pairs. The three oxygen atoms are bonded symmetrically around the central sulfur atom and it has both n electron arrangement and a molecular shape of trigonal planar.

For SO3 we would expect bond angles of 120 degrees. The lone pairs on SO2 are more repulsive and therefore we would expect a bond angle slightly less than 120 on the SO2 molecule.

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