Question

Describe the shapes of BF₃ and BH₄^–. Assign the hybridisation of boron in these species.

Answer 1

BF₃

As a result of its small size and high electronegativity, boron tends to form monomeric covalent halides. These halides have a planar triangular geometry. This triangular shape is formed by the overlap of three sp² hybridised orbitals of boron with the sporbitals of three halogen atoms. Boron is sp² hybridised in BF₃.

BH₄^–

Boron-hydride ion (BH₄^–) is formed by the sp³ hybridisation of boron orbitals. Therefore, it is tetrahedral in structure