Question

This should be a quick one--why is the oxidation state of Mn in MnO4 +7? Is it that we're dealing w/ Mn(III), and that there are 4 O atoms?

Answer 1

if Mn is +7, then there must be a negative charge on the ion. MnO4^-

Answer 2

So we've got 2 for each of the oxygen, for (2*4)=8, and we know that permanganate has a charge of -1. Is that it?

Answer 3

yep -2 for each oxygen.. total of -8, if you know what Mn is +7, the ion MUST have a charge of -1.