Electronic Theory of Valency





The electronic theory of valency was originated by Kossel and Lewis (1916) independently and applied by Langmuir (1919). According to this theory, every element has a tendency to occupy inert electronic configuration (ns^2np^6) of the nearest inert gas, because it is considered as the most stable configuration (stable octet).

This configuration is attained by either

(i) transference of electrons,

(ii) sharing of electrons or

(iii) donation of lone pair of electrons.

Types of bonds in a molecule which are discussed below:

There are three types of bonds between atoms in a molecule which are discussed below:

1. Ionic or Electrovalent Bond or Kernel Bond: such type of bond is formed by the transference of one or more electrons form one atom to the other and consequently former becomes cation and the latter becomes anion.

- Ionic bond is called kernel bond because during formation of cation outer-most orbit is destroyed and the remaining part in called core or kernel.

- Nature of ionic bond is electrostatic force of attraction and it is non directional bond.

- Ionic bond was introduced by Kossel.

The formation of ionic bond depends upon three major factors:

(i) Ionization potential: the lower the value of ionization potential, the greater will be the ease of formation of cations.

(ii) Electron affinity: the higher the electron affinity the greater is the ease of formation of anions.

Electron affinity

 

(iii) Lattice energy: the higher the value of lattice energy of resulting ionic compound greater will be the ease of its formation.



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