Question

what is oxidation number?

Answer 1

It is a number assigned to an element in chemical combination that represents the number of electrons lost.

Answer 2

Oxidation number is the charge that an atom appears to have when the electrons are distributed according to certain rules.
The rules are as follows
1. In free elements, each atom has an oxidation number of 0.
2. The sum of the oxidation numbers of all the atoms in a molecule is 0.
3. The oxidation number of a simple ion containing one atom is equal to the charge on the ion.
4. The sum of the oxidation numbers of all atoms in a complex ion is equal to the charge on the ion
5. Hydrogen has an oxidation number of +1 in it's compounds except in metallic hydrides.
6 Oxygen has an oxidation numbers of -2 in it's compounds.
7. The oxidation number of group 1 elements in their compounds is always +1 and the oxidation number of group 2 elements in their compounds is always +2.
8. The oxidation number of a halogen when bonded to a less electronegative atom is -1
remember......it is between oxidation numbers in oxides and oxidation numbers in hydrides.