# What is ionic size used for?

Jul 31, 2017

Ionic size is used to compare melting point, boiling point, solubility, thermal stability etc.of ionic compounds.

#### Explanation:

Ionic size is a one of the factors used in determining the polarization of a cation or an anion in a compound.Polarization is the distortion of the electron cloud of an atom.The ability of an ion to polarize other ions is called polarizing power.The ability of an ion to get polarized is called polarizability.Due to their small size, cations polarize other ions while anions due to their large electron cloud and so large size get polarized.

The polarization of a cation or anion is determined using Fajan's rules which are:

Polarization $\alpha$ product of charges of anion and cation

Polarization $\alpha \left(\text{covalent character")/("Ionic character}\right)$

Polarization $\alpha \left(\text{size of anion")/("size of cation}\right)$

This polarization can be used to compare the various properties of ionic compounds such as melting point, boiling point, solubility and thermal stability