The oxidation number of Mn is +7.
The oxidation number of O in compounds is usually -2, but it is -1 in peroxides.
The oxidation number of a Group 1 element in a compound is +1.
The sum of the oxidation numbers of all of the atoms in a neutral compound is 0.
Rule 1 states that the oxidation number of
O is -2. We write the oxidation number of the element above its symbol and the total for 3