AS CHARGE DOMINATESIN ALCL3 LATTICE E. MUST B MORE SO IT MST B MOST IONIC BUT IT COVALENTPLZ EXPLN THE ANSWR WITH REF 2 NACL MgO IN DTAIL

Dear raj,

FAJAN RULE SAYS THAT DISTORTION OF ELECTRON CLOUD TAKES PLACE WHEN SIZE OF THE CATION IS SMALLER THAN ANION . WHAT IF ITS REVERSE THAT IS SIZE OF ANION IS SMALLER THAN CATION FOR EXAMPLE CESIUM FLUORIDE. HOW DO WE EXPLAIN ITS IONIC NATURE THOUGH HERE ALSO THERE SHOULD BE DISTORTION.

According to fajan's rule condition for ionicity of a bond is

large cation small anion

reason: A  cation is formed by loosing an electron as we go lower down the group size inc and I.E decreases and anion is formed by gaining an electron

E.A decreases as we go down a group so small size = high E.A

also small cation polarizes to greater extent as compared to large  cation

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according to fazane rule  the charge of Al is +3..........  Al is small size element.....................  Cl is relatively bi size element...........  so comparitively AlCl3 al will more attract cl than NaCl OR MgO ...  so the shape gets disorder............... and more covalent character shows............