Question

What do you mean by valency?

Answer 1

Valency:

• Valency of an element is the number of electrons lost or gained or shared with other atoms in the formation of compounds.
• The electrons that are present in the outermost shell are known as valence electrons.
• The valency of representative elements is equal to the number of electrons in the outermost shell for groups 1 and 2, for groups 13 and 14 subtract 10 from group number and 8 minus the number of electrons in the outer most shell for groups 15- 18.
• Inert gases like He,Ne,Ar,Kr,Xe, etc ( which are belongs to 18th group elements ) normally do not enter into chemical bonding and hence their valency is zero.

Example 1:

• Consider the Lithium $\left(\mathrm{Li}\right)$ atom having an atomic number $3$ and it belongs to I A group element
• The electronic configuration of Lithium $\left(\mathrm{Li}\right)$ is$1{\mathrm{s}}^{2}2{\mathrm{s}}^1$.
• The number of valence electrons in lithium is $1$. Thus, it must lose one to attain stability ( To get more stable electronic configuration of inert gas). Therefore, the valency of Lithium $\left(\mathrm{Li}\right)$ is $1$.

Example 2:

• Consider the Nitrogen $\left(N\right)$ atom having an atomic number $7$ and it belongs to 15 A group element
• The electronic configuration of Nitrogen $\left(N\right)$ is$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^3$.
• The valency of Nitrogen $\left(N\right)$ is 3 as it gains 3 electrons to get more stable inert gas Neon $\left(\mathrm{Ne}\right)$ configuration.