Polarizability is defined as the tendency of an ion to be polarized.
Distortion of negatively charged ion by the positively charged ion is called polarizability.
Extent of polarization is given by Fajan's Rule.
Fajan's rule- It can be stated by three postulates
Size of ion- If the size of the cation is small and the anion is large, the more will be the covalent character of the ionic bond.
Charge of cation-More the charge, the more will be the covalent character of the ionic bond.
Electronic configuration- The cations of the same size, one belonging to transition metals having electronic configuration have greater covalent character than the one with electronic configuration belongs to alkaline earth metals.
Factors affecting polarizability
Molecular size- As the size of the molecule increases, the polarizability also increases.
The number of electrons present- More the number of electrons more will be the polarizability.