Which of the following species contains three bond pairs and one lone pair around the central atom?

Question

Accepted Answer

1.  **Analyze PCl₃ (Phosphorus Trichloride):** The central Phosphorus atom (Group 15) has 5 valence electrons. It forms 3 sigma bonds with Chlorine atoms. 
    - Bond Pairs (BP) = 3
    - Lone Pairs (LP) = $\frac{5 - 3}{2} = 1$
    - **Result:** 3 Bond Pairs + 1 Lone Pair.

2.  **Analyze H₂O:** Oxygen (Group 16) has 6 valence electrons. Forms 2 bonds with Hydrogen.
    - BP = 2
    - LP = $\frac{6 - 2}{2} = 2$
    - Result: 2 BP + 2 LP.

3.  **Analyze BF₃:** Boron (Group 13) has 3 valence electrons. Forms 3 bonds with Fluorine.
    - BP = 3
    - LP = $\frac{3 - 3}{2} = 0$
    - Result: 3 BP + 0 LP.

4.  **Analyze NH₂⁻:** Nitrogen (Group 15) has 5 valence electrons. The negative charge adds 1 electron, total 6. Forms 2 bonds with Hydrogen.
    - BP = 2
    - LP = $\frac{6 - 2}{2} = 2$
    - Result: 2 BP + 2 LP.

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