Question

How do we calculate the oxidation number of polyatomic ion?

• A. Add individual negative oxidation numbers only and calculate final value
• B. Add individual oxidation numbers and calculate final value as polyatomic ion oxidation number
• C. Add individual positive oxidation numbers only and calculate final value
• D. None of the choices

Answer 1

The correct option is B

Add individual oxidation numbers and calculate final value as polyatomic ion oxidation number

The sum of the oxidation numbers of the atoms present in a polyatomic ion is equal to the charge of the ion.

Individual ionic oxidation numbers are added up and the resultant balance number is taken as final oxidation number.

${S{O}_4}^{-2}$

S = + 6 and O = - 2 (oxidation numbers)

(+6) + [(-2) * (4)] = (+6) + (-8) = - 2