Which of the following species has a bond angle of 120$$^\circ$$?

Question

Accepted Answer

1. **Analyze BCl$$_3$$:** The central Boron atom has 3 valence electrons. It forms 3 sigma bonds with Chlorine atoms and has zero lone pairs. According to **VSEPR theory**, a molecule with 3 bond pairs and 0 lone pairs (AB$$_3$$ type) adopts a **trigonal planar** geometry. The hybridisation is **sp$$^2$$** and the bond angle is exactly **120$$^\circ$$** .
2. **Analyze other options:**
   - **SF$$_6$$:** Sulphur is sp$$^3$$d$$^2$$ hybridised with octahedral geometry. Bond angles are 90$$^\circ$$ .
   - **NCl$$_3$$:** Nitrogen is sp$$^3$$ hybridised with 1 lone pair (Pyramidal geometry). Bond angle is less than 109.5$$^\circ$$ .
   - **PH$$_3$$:** Phosphorus is sp$$^3$$ hybridised (or unhybridised per Drago's rule) with 1 lone pair. Bond angle is close to 93$$^\circ$$ (Pyramidal) .
3. **Conclusion:** Only BCl$$_3$$ has a bond angle of 120$$^\circ$$.

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