State Fajan's rules, and give suitable examples.

Explanation

Fajan.s rule 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 thebond increases.
Ex: The ionic nature among alkali metals ions follows the order: `Li^(+)ltNa^(+)ltK^(+)ltRb^(+)ltCs^(+)`
b. Ionic bond is favoured with a small anion.
Ex: Out of `CaF_(2)` and` CaI_(2),CaF_(2)` is more ionic, as the size of `F^(-)` ion is smaller than that of `I^(-)` ion. Size `F^(-)ltI^(-)`
3. Smaller charge on cation or anion or both the ions, favours the formation of ionic bond.
Ex: NaCl is more ionic 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^(+)(2,8,8)` has inert gas configuration.
`CuCl` is more covalent since `Cu^(+)` (2,8,8) has pseudo inert gas configuration.