# What are the oxidation numbers for CuSO_4?

For $\text{cupric sulfate}$? Well, there is a $C u \left(I I\right)$ ion.
And for the $\text{sulfate counterion}$, sulfur takes a $V I +$ oxidation state. And, as usual, the $O$ atoms takes a $- I I$ oxidation state. Again, as normal, the weighted sum of the oxidation numbers for a neutral species is $\text{ZERO} : 0 = 4 \times \left(2 -\right) + 2 + 6$.