Answer:
The sum of all the oxidation numbers for neutral compound = 0
For charged species sum of oxidation no. of all the elements is not equal to zero either positive or negative.
Explanation:
In case for neutral compounds sum of total oxidation no. of all elements is equal to zero.
Let us consider for
K₂Cr₂O₇ (Potassium dichromate) the sum of total oxidation state of elements is equal to zero.
Oxidation state of potassium = +1, For Chromium = +6 & for oxygen = -2
So total oxidation number
2 x (+1) + 2 x (+6) + 7 x (-2)
= +14 - 14 = 0.
In case for charged species.
Example for
Ammonium ion (NH₄⁺) total charge = +1
∵ O.N for nitrogen = -3 and for hydrogen = +1
∴ Sum of oxidation numbers = 1 x (-3) + 4 x (+1)
= +1
For Carbonate ion (CO₃²⁻) total charge = -2
Oxidation number for carbon = +4 and for oxygen = -2
(∵Oxygen is more electronegative than carbon)
∴ Sum of oxidation numbers = 1 x (+4) + 3 x (-2) = -2
