Question

What is the average bond order in the sulfate ion?

Answer 1

Bond order

• The number of chemical bonds between two atoms is represented by the bond order.
• For examples, the bond order of diatomic nitrogen ${\mathrm{N}}_2\left(\mathrm{N}\equiv \mathrm{N}\right)$ is three.
• The bond order describes the stability of the bond.

Average bond order of sulfate ion

• Structure of sulfate ion $\left({\mathrm{SO}}_4^{2-}\right)$:

• There are six equivalent contributors to the sulfate ion because they are all equivalent.
• There are six bonding electron pairs and four atoms bound to the Sulfur atom in each resonance contributor.
• The bond order of sulfate ion is as follows:

$\begin{array}{rcl}\mathrm{Bond}\mathrm{order}& =& \frac{\mathrm{Nunber}\mathrm{of}\mathrm{bonding}\mathrm{electron}\mathrm{pairs}}{\mathrm{Nunber}\mathrm{of}\mathrm{bonding}\mathrm{atoms}}\\ & =& \frac{6}{4}\\ & =& 1.5\end{array}$

• Therefore, the average bond order of sulfate ion is $1.5$.