What is the use of valency in chemistry.

Dear Student Valency is the combining capacity of an element. It is the number of electrons in an atom that actually take part in bond formation. The number of valence electrons is the valency of the element. For example, carbon atom with an atomic number 6 has 4 valence electrons. K-shell = 2 electrons, L-shell = 4 electrons. Thus Carbon atom is capable of forming 4 bonds. Hence its valency or combining capacity is four. Regards