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Answer 1 · 2014-06-23T12:37:12

The sulfate ion should have shorter sulfur-oxygen bonds than a sulfite ion.

The sulfite ion is a resonance hybrid of three equivalent contributing structures.

www.wiley.com

The bond orders of the #"S-O"# bonds in any one contributor are 2, 1, and 1.

The bond orders of the #"S-O"# bonds in the hybrid are an average of these numbers.

#BO = #2 + 1 +1)/3 = 4/3 = 1.33#

The sulfate ion is a resonance hybrid of six equivalent contributing structures.

faculty.chem.queensu.ca

The bond orders of the #"S-O"# bonds in any one contributor are 2, 2, 1, and 1.

The bond orders of the #"S-O"# bonds in the hybrid are an average of these numbers.

#BO = (2 + 2 + 1 +1)/4 = 6/4 = 1.50#

The greater the bond order, the shorter the bond length.

The #"S-O"# bond order is greater in the sulfate ion, so sulfate ions should have shorter #"S-O"# bonds.

Experiments confirm this prediction.

The measured #"S-O"# bond lengths are 149 pm in sulfate ion and 151 pm in sulfite ion.