State Fajan's rules, and give suitable examples.

Explanation

Fajan's rules are applied to predict the nature of bond in a molecule.
Fajan's rules :
1) As the size of cation increases, the ionic nature of the bond increases.
Ex : The ionic nature among alkali metal ions follows the order : `L1^(+) lt Na^(+) lt K^(+), lt Rb^(+) lt Cs^(+)`
Ionic bond is favoured with a small anion.
Ex : Out of `CaF_(2) " and " Ca1_(2), CaF_(2)` is more ionic, as the size of `F^(-)` ion is smaller than that of `I^(-)` ion. size : `F^(-) lt I^(-)`.
Smaller charges on cation or anion or both the ions, favours the formation of ionic bond.
3) Smaller charges on cation or anion or both the ions, favours the formation of ionic bond.
Ex : NaC1 is more than `AlCl_(3)` as the charge on `Na(Na^(+))` is less than that on `Al(Al^(+3))`.
4) Cations with inert gas configuration form ionic bonds, while cations with pseudo inert gas configuration favour covalent bond formation.
Ex : NaCl is ionic, since `Na^(+)(2,8,underline(8))` has inert gas configuration.
CuCl is more covalent, since `Cu^(+)(2,8,underline(8))` has pseudo inert gas configuration.