Question

Why is it important to know the valencies to write a chemical formula?

Answer 1

Valency

• Valency is known as the combining capacity of an atom with another atom during a chemical reaction.
• The valency of an element can be defined as the number of outermost electrons in the valence shell or the number of electrons needed to complete the octet configuration or the valence shell
• Valency can also be defined as the number of electrons gained or lost by the elements during a chemical reaction to attain stability.
• The knowledge about valency is necessary to know how the atoms are combined during a chemical reaction.

• For example, take NaCl (sodium chloride), lets's see how sodium and chloride combine.
• The outermost electronic configuration of sodium is 2,8,1 & the valency is 1. It donates an electron since it is an electropositive atom.
• The outermost electronic configuration of chlorine is 2,8,7 & the valency is 1. It receives an electron since it is an electronegative atom.
• Therefore one sodium combines with one chloride to form NaCl (sodium chloride).