Describe Formation and Structure of Boron Trichloride by Hybridization

Formation and structure of Boron Trichloride (BCI₃₎ molecule: The electronic configuration of boron (5) is 1s² 2s² 2p_x¹ 2p_y⁰ 2p_z⁰. When one electron is transferred from 2s orbital to 2p orbital, it has three unpaired electrons, which explains the valency of three for boron. The sp² hybridization takes place on boron atom.

At normal state, B (5): 1s² 2s² 2p_x¹ 2p_y⁰ 2p_z⁰

At excited state. B* (5): 1s² 2s¹ 2p_x¹ 2p_y⁰ 2p_z⁰

After sp² hybridization, B (5): 1s² ψ₁¹ ψ₂¹ ψ₃¹

Where ψ₁, ψ₂ and ψ₃ are hybrid orbitals. They overlap with 3p_z orbitals (Containing one electron each) of three chlorine atoms as follows and form three B-CI bonds. Then BCl₃ molecule is formed.

So, Boron Trichloride (BCl₃₎ is a planar molecule, where all bond angles are 120⁰. Although each B-Cl bonds is polar, the vector summation of three dipoles is zero and Bell has a zero dipole moment.