Which of the following species contains three bond pairs and one lone pair around the central atom ?
- H2O
- BF3
- NH2-
- PCl3
Answer
(4) PCl3
Solution
H2O: 2 bond pairs + 2 lone pairs on O.
BF3: 3 bond pairs + 0 lone pair on B.
NH2-: 2 bond pairs + 2 lone pairs on N.
PCl3: P has 5 valence electrons; 3 are used in P–Cl bonds ⇒ 3 bond pairs + 1 lone pair (pyramidal).
Answer: (4)