Hybridization of Boron Trifluoride (BF₃) - sp2

Introduction

Boron trifluoride (BF₃) is trigonal planar with 120° bond angles. Boron has only 3 valence electrons and forms 3 bonds — leaving an empty p orbital that makes it a powerful Lewis acid.

Electron Configuration

Boron has 3 valence electrons: 2s² 2p¹. In the ground state, only one p orbital has an electron. Hybridization mixes the s and two p orbitals to create three equivalent bonding orbitals.

Atomic Orbitals

The 2s orbital is spherical. Two p orbitals (pₓ and pᵧ) participate in hybridization. The 2pᵩ orbital stays empty and unhybridized, perpendicular to the molecular plane.

Orbital Mixing

One s and two p orbitals combine to form three sp² hybrids. Unlike ethene or formaldehyde, the leftover p orbital here is empty — no π bond forms.

Result

Three sp² orbitals at 120° in a plane. The empty pᵩ orbital is perpendicular to the plane. This empty orbital is why BF₃ is electron-deficient and acts as a Lewis acid.

Bonding

Each sp² orbital overlaps with a fluorine orbital to form a σ bond. The empty p orbital can accept an electron pair from a Lewis base like NH₃, forming an adduct.

Related Topics