So I'm being asked to find the chemical formula for copper(II) sulfate.

I thought it would be written as:


Apparently it's written as:


Can anyone please explain to me why the latter answer is correct?


The sulfate anion, $\ce{SO4^{2-}}$ has a charge of -2. Copper can have cations with either +1 or +2. So the two possible copper sulfates are cuprous sulfate (copper(I) sulfate), $\ce{Cu2SO4}$, and cupric sulfate (copper(II) sulfate), $\ce{CuSO4}$.


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