Answer:
+7
Explanation:
Within every molecule, there is always an oxidation number assigned to every individual atom within the molecule. Hydrogen will always have an oxidation number of +1 (because it only has one electron to give, and when it gives that electron, it has a charge of +1).
Elements in group 1 always have an oxidation number of +1, and elements in group 16 always have an oxidation number of -2. Using this information we can calculate the oxidation number of Mn in the molecule KMnO₄.
Overall the molecule is neutral, so all the oxidation numbers would add up to zero:
K + Mn + O₄ = 0
(+1) + Mn + 4(-2) = 0
(+1) + Mn + (-8) = 0
Mn + (-7) = 0
Mn = +7
