Chemical Bonding! (1)
Chemistry
Level
3
Which Halide of aluminium has lowest melting point?
Chloride
Iodide
Fluoride
Bromide
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1 solution
Al+3 has very high charge hence it has very high polarising power. Its one of the cations which can even polarise fluoride and oxide ions to some extent. In its halides the order should be governed by the percentage covalent character hence the order of melting point should be Fluoride>Chloride>Bromide>Iodide.
But actually Iodide and bromide exchange there positions here because of Vander Waal's forces.
Iodide of aluminium has very high molecular weight which is responsible for its melting point to increase over Bromide due to increased Vander Waal's forces
The Correct order is Fluoride>Chloride>Iodide>Bromide