Q.Explain the covalent character in ionic bond.

Just as covalent bonds can carry partial ionic character (see Dipole Moment and Bond Polarity), formally ionic compounds can carry partial COVALENT character — evidenced, for instance, by lithium chloride's solubility in organic solvents such as ethanol, a property normally associated with covalent, not ionic, compounds.

The mechanism is polarisation: in an ionic compound, the cation's positive charge attracts the neighbouring anion's valence electron cloud (while repelling its nucleus), distorting that cloud so that some electron density drifts toward the cation — producing partial sharing, i.e. partial covalent character. A cation's ability to cause this distortion is its polarising power; an anion's tendency to be distorted is its polarisability.

Fajans' rules predict how much polarisation (and hence covalent character) results:

1. Higher ionic charge → more covalent character. A higher-charged cation pulls the anion's cloud more strongly, and a higher-charged anion is itself more polarisable; increasing the charge on EITHER ion increases covalent character. Since cationic charge rises Na⁺ < Mg²⁺ < Al³⁺, covalent character rises in the same order: NaCl < MgCl₂ < AlCl₃. …