Describe the change in hybridisation (if any) of the Al atom in the following reaction.


The valence orbital picture of aluminum in the ground state can be shown as:


The orbital picture of aluminum in the excited state can be shown as:



Hence, it undergoes sp2 hybridization to give a trigonal planar arrangement (in AlCl3). To form AlCl4, the empty 3pz orbital also gets involved and the hybridization changes from sp2 to sp3. As a result, the shape becomes tetrahedral.


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