What is the sum of the oxidation numbers of all of the atoms in a neutral compound?
The oxidation number for an element expresses the oxidation state of that element.
Let us consider three examples, potassium permanganate,
hypochlorite ion, ammonium ion
In the first case, potassium permanganate, KMnO4, the oxidation number is 0 (neutral).
K= + 1 Mn= + 7 O = -2.
So if you have K ( +1) + Mn( + 7) and O4 (-8)
The sum is zero
In charged polyatomic ions, the sum equals the charge of the polyatomic ion
The hypochlorite ion, ClO-, has a negative sum.
Cl = + 1 and the O = -2
The ammonium ion, NH4+, has an oxidation sum of + 1
N= - 3 and H ( 4 x + 1) = + 1.