I would like to know if the following statement is true or false.

Question

In the molecule MnO2, the oxidation number of Mn is +4.

Answer 1

Yes. The molecule is assumed to be neutral, or 0. For this to be the case, Mn would have to have a +4 charge to balance out the 2 O^-2.

Mn + 2O = 0

1(+4) + 2(-2) = 0

4 + -4 = 0

0 = 0

Answer 2

MnO2

oxidation number of O is almost always -2, so, 2 x -2 = -4

oxidation number of Mn + -4 = 0

oxidation number of Mn is +4