Paul J. answered • 06/14/21
Chemistry Tutor/Bachelor's of Science in Forensic Chemistry
In order to answer this question, you need to know how to determine the oxidation state of copper. The oxidation state (or oxidation number) is an integer that represents the number of electrons either lost or gained by an atom assuming all of the bonds formed by the atom are completely ionic. An easier way of defining oxidation state is the hypothetical charge of the atom.
We know the sulfate (SO4) anion has a formal charge of -2, however we don't know the "charge" of copper. To determine the oxidation number of copper, we can set up an algebraic expression:
2 Cu + SO4 = 0
We then substitute in the charges of each species into the expression (I'm going to set copper to x because we don't know the charge "aka oxidation state" of copper:
2 x + -2 = 0
If you add 2 to 0 and then divide 2 by 2, x will come out to equal +1, which indicates each copper atom has a hypothetical charge of +1.
Since you have two copper atoms present and each has a +1 charge, they will cancel out the -2 charge on the sulfate ion, so copper (I) sulfate does not have a formal charge.
