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

Question

Philoid · Accepted Answer

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.