Question

What are the oxidation numbers for `CuSO_4`?

Answer 1

For `"cupric sulfate"`? Well, there is a `Cu(II)` ion.

Explanation:

And for the `"sulfate counterion"`, sulfur takes a `VI+` oxidation state. And, as usual, the `O` atoms takes a `-II` oxidation state. Again, as normal, the weighted sum of the oxidation numbers for a neutral species is `"ZERO": 0=4xx(2-)+2+6`.