Rules to find Oxidation Number

Rules to find Oxidation Number

• The O.N. of all the elements in its uncombined state or elementary state is zero.
• O.N. of an element in a mono-atomic ion is equal to the charge present on the ion.
• O.N. of Fluorine in all its compounds is -1. (Fluorine is the most electronegative element).

Rules to find Oxidation Number

• O.N. of alkali metals is +1 (Group 1: Li, Na, K)
• O.N. of alkaline earth metals is +2 (Group 2: Mg, Be, Ca, Ba, Sr)
• O.N. of Hydrogen in all its compounds is +1
• In case of Hydrides, O.N. of Hydrogen is -1 (NaH, BeH2, CaH2...)
• O.N. of Oxygen in all its compounds is -1.

Rules to find Oxidation Number

• The sum of all the O.N. of all the atoms in a molecule must equate to zero.
• The sum of all O.N. of all the atoms in a molecule equates to the charge present in that ion.