# How do we represent the "sulfate ion"?

$S {O}_{4}^{2 -}$
The elements composing the $S {O}_{4}^{2 -}$ are located in Group 16 which have 6 valence electrons each and both are nonmetallic. This means that these elements have the tendency of sharing their electrons to achieve stability.
Sulfur shares its 6e- to 3 Oxygen atoms to complete the octet leaving 1 Oxygen with only 6. The oxidation number of $- 2$ for this covalently bonded ion signifies that it has gained 2e- to complete the octet of the other Oxygen atom.