What are Fajan’s Rule?

The extent of polarization depends upon the polarization power of the cation and the polarizability of the anion.

There are the following rules:

1. Small positive ion favours covalency.
2. A lagre negative ion favours covalency.
3. High charge on either ion or on both ions favours covalency.
4. Cations with inert gas configuration have low polarization power.