Among H ₂ ~S , H ₂ O , NF ₃, NH ₃ and CHCl ₃ , identify the molecule ( X ) with lowest dipole moment value. The number of lone pairs of electrons present on the central atom of the molecule (X) is :

Step-by-step solution

Comparing dipole moments: H₂S ≈ 0.97 D (bent, 2 lone pairs on S), H₂O ≈ 1.85 D (bent, 2 lone pairs on O), NF₃ ≈ 0.24 D (pyramidal, 1 lone pair on N), NH₃ ≈ 1.42 D (pyramidal, 1 lone pair on N), CHCl₃ ≈ 1.04 D (tetrahedral, 0 lone pairs on C). NF₃ has the lowest dipole moment because the highly polar N-F bonds are oriented in such a way that their contributions nearly cancel with the effect of the lone pair. The central atom in NF₃ is N, which has 1 lone pair of electrons.