State Fajan's rules, and give suitable examples.

Explanation

"A." 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 : `Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)`
2) 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^(-) lt I^(-)`
3) Smaller charges on cation or anion or both the-ions, favours the formation of ionic bond.
Ex: Had 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: HaCl is idnic,.since `Na^+` (2,8, 8) has inert gas configuration. CuCl is more covalent, since `Cu^+` (2, 8, 8) has pseudo inert, gas configuration.