MN in (MNO4)-2

The oxidation state of oxygen in (MNO4)-2 is -2. This is because oxygen typically has an oxidation state of -2 in most compounds. In the case of (MNO4)-2, the overall charge of the ion is -2, so the oxidation state of oxygen can be calculated as follows:

Let x be the oxidation state of Mn.
Let y be the oxidation state of oxygen.

The sum of the oxidation states must equal the charge of the ion:
x + 4y = -2

Since oxygen has an oxidation state of -2, we can substitute -2 for y in the equation:
x + 4(-2) = -2
x - 8 = -2
x = 6

Therefore, the oxidation state of Mn in (MNO4)-2 is +6.