how to draw lewis structure? explain fajan rule.

explain vsepr theory

Few ionic bonds have partial covalent characteristics which were first discussed by a scientist, Kazimierz Fajans in 1923. In the time with the help of X-ray crystallography, he was able to predict ionic or covalent bonding with the attributes like ionic and atomic radius.

He gave the rule to predict whether a chemical bond will be covalent or ionic which is now commonly known as Fajan’s rule.

Fajan’s rules

The rule can be stated on the basis of 3 factors, which are:

1. Size of the ion: Smaller the size of cation, larger the size of the anion, greater is the covalent character of the ionic bond.
2. Charge of Cation: Greater the charge of cation, greater is the covalent character of the ionic bond.
3. Electronic configuration: For cations with same charge and size, the one, with (n-1)dn nso which is found in transition elements have greater covalent character than the cation with ns2 np6 electronic configuration, which is commonly found in alkali or alkaline earth metals.

The covalent character is found in compounds which have high polarizing cation and high polarizable anion.