Explain the following : Aluminium forms [AlF_6]^(3-) ion but boron does not form [BF_6]^(3-) ion.

Explain the following : Aluminium forms [AlF_6]^(3-) ion but boron doe

1.	Explain the following : Aluminium forms [AlF_6]^(3-) ion but boron does not form [BF_6]^(3-) ion.
Answer» Solution :Al has vacant .d. orbitals and can EXPAND its co-ordination no. and forms `[AlF_6]^(3-)` . On the other hand, BORON does not have .d. orbitals and cannot form `[BF_6]^(3-)` and cannot expand its covalence beyond 4 and thus , GIVES `[BF_4]^-`