Boron trichloride (BCl3)

Boron trichloride, BCl3, is a covalent molecule in which the central boron atom is sp2 hybridised, using its three hybrid orbitals to form three B-Cl sigma bonds while leaving one unhybridised p-orbital on boron completely empty. Because boron contributes only three electrons to bonding and has no lone pair to complete its octet, boron in BCl3 has an incomplete octet — just six electrons around it rather than eight. The three Cl atoms and the central B atom all lie in one plane, spread symmetrically at 120° to each other, so BCl3 is a trigonal planar, nonpolar …