# Question d81d0

Jun 23, 2014

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

#### Explanation:

The sulfite ion is a resonance hybrid of three equivalent contributing structures. The bond orders of the $\text{S-O}$ bonds in any one contributor are 2, 1, and 1.

The bond orders of the $\text{S-O}$ bonds in the hybrid are an average of these numbers.

$B O =$2 + 1 +1)/3 = 4/3 = 1.33

The sulfate ion is a resonance hybrid of six equivalent contributing structures. The bond orders of the $\text{S-O}$ bonds in any one contributor are 2, 2, 1, and 1.

The bond orders of the $\text{S-O}$ bonds in the hybrid are an average of these numbers.

$B O = \frac{2 + 2 + 1 + 1}{4} = \frac{6}{4} = 1.50$

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

The $\text{S-O}$ bond order is greater in the sulfate ion, so sulfate ions should have shorter $\text{S-O}$ bonds.

Experiments confirm this prediction.

The measured $\text{S-O}$ bond lengths are 149 pm in sulfate ion and 151 pm in sulfite ion.