# In the sulfate ion (SO_4^(2-)), how many electrons are available for bonding?

Dec 3, 2016

There are $5 \times 6 + 2 = 32$ $\text{valence electrons}$, distributed around 5 centres. $12$ electrons are formally involved in bonding.

#### Explanation:

A typical valence bond representation of the $\text{sulfate dianion}$ is as ""^(-)O_2S(=O)_2 (this derives from the parent sulfuric acid, ${\left(H O\right)}_{2} S {\left(= O\right)}_{2}$). Around the sulfur centre there are 6 valence electrons, participating in single or multiple $\text{sulfur-oxygen}$ bonds.

What is the geometry around sulfur?

A representation of (HO)_2""S^(2+)(O^-)_2 is also feasible, but the sulfur oxygen double bonds are usually depicted.

Note that the electron count was simply obtained by the operation $5 \times 6 + 2 = 32$ $\text{valence electrons}$. Why did I add an additional 2 electrons?