Predict the change, if any, in hybridization of Al atom in the following reaction `AlCl_(3)+Cl^(-) rarr AlCl_(4)^(-)`.

Explanation

1) `AlCl_(3)` is mostly covalent.
2) In `AlCl_(3)underset(Cl)underset(|)((Cl-Al-Cl))`, Al atom undergoes `sp^(2)` hybridisation. The molecule is trigonal planar. It has 3 bond pair of electrons and no lone pair of electrons.

3) In `AlCl_(3)`, the central atom of Al has vacant p-orbitals. So it can accept a lone pair of electrons from `Cl^(-)` ion and form the complex `AlCl_(4)^(-)` ion.

`therefore Al(sp^(2))Cl^(3) rarr Al(sp_(3))Cl^(-)`
`AlCl_(4)^(-)` has tetrahedral structure. Al atom undergoes `sp^(3)` hybridisation. There are 4 bond pair of electrons and no lone pair of electrons in `AlCl_(4)^(-)` ion.