Oxidation number of mno4

Solution

Let oxidation number of Mn be x.
We know that, Ox. no. of O=−2.
So, Ox. no. Mn+ 4(Ox. no. O)=−1
x+4(−2)=−1
or x−8=−1
or x=+8−1=+7
The oxidation number of Mn in [MnO
4
​
]
−
ion is +7.