Question

How can you memorize oxidation number rules?

Answer 1

Oxidation number is the number of electrons that an atom loses or gains to form a chemical bond. If we know the type of compound, we will easily know the oxidation number of compounds.

Complete step by step answer:
Now, let’s discuss some rules of calculation of oxidation number.

1. If a compound exists in elemental form (only one type of atoms present), the oxidation number of the element is always zero.
2. For a neutral compound, summation of oxidation states of all atoms in the compound is equal to zero.
3. For ions, the charge indicates the oxidation number. For example, the oxidation number of chloride ions is -1.

Additional Information:
Let’s discuss some important points regarding oxidation states.
1)All the halogen atoms except fluorine possess more than one oxidation state, such as, -1,+1, +3,+5,+7 but oxidation state possessed by fluorine is -1
2) It is a point of confusion about different oxidation states of oxygen. We know that, generally oxygen possesses an oxidation state of -2 because it can accept two electrons to fulfill its valence shell electronic configuration to make bonds.

Note: Students have to take care of taking the oxidation number of hydrogen in the calculation of an oxidation number of an element. When a hydrogen atom is bonded to a non-metal, its oxidation number is +1 and when it is bonded to a metal, its oxidation number is -1. In ${{\text{H}}_2}{\text{S}}$, hydrogen is bonded to a non-metal (sulphur), so its oxidation number is +1.