Question

While finding oxidising number which valency should be considered positive or negative

Answer 1

Rules for finding oxidation number

1. The oxidation number of a free element is always 0.

2. The oxidation number of a monatomic ion equals the charge of the ion.

3. The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements.

4. The oxidation number of O in compounds is usually -2, but it is -1 in peroxides.

5. The oxidation number of a Group 1 element in a compound is +1.

6. The oxidation number of a Group 2 element in a compound is +2.

7. The oxidation number of a Group 17 element in a binary compound is -1.

8. The sum of the oxidation numbers of all of the atoms in a neutral compound is 0.

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