Chemistry Q&A

Why is BF₃ sp² hybridised?

Answer

In BF₃, boron forms three σ bonds with fluorine and has no lone pair, so its steric number is 3, which corresponds to sp² hybridisation and a trigonal planar shape.

Explanation

Boron’s valence shell in BF₃: three bonding pairs, zero lone pairs.

Steric number 3 → three sp² hybrids at 120° in a plane.

BF₃ is often described as electron-deficient (incomplete octet on boron), which is related but separate from the hybridisation label.

Example · Compare with NH₃ (steric number 4 → sp³, pyramidal) where nitrogen has a lone pair.

Common Student Mistake: Thinking BF₃ is sp³ because boron “needs” four orbitals — geometry and Lewis structure decide hybridisation.

Relevant for: BOARDS · JEE · NEET