I was going through the topic of 'ionic bond' and read this:

No bond is 100% ionic in character. It has some percentage of covalent character.

I didn't understand how an ionic bond can be partially covalent in character. Please explain along with an example.


One way is Polarization. When a small cation approaches a large anion it distorts the charge density towards itself thereby forming a type of bond which has directional characteristic i.e from ** (-) ----> (+) ** which is characteristic of a covalent bond.

This polarization has some rules given by **Fajan **

  1. Smaller the cation better distortion/polarization.
  2. More the amount of positive charge more is the polarization.
  3. or more the charge : radius ratio of cation more is the polarization.

So in short every cation has the power of polarization and therefore no bond is 100% ionic.


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