Which one of the following molecules has maximum dipole moment?
- CH4
- NF3
- NH3
- PF5
Answer
(3) NH3
Solution
CH4 (tetrahedral) and PF5 (trigonal bipyramidal) are symmetrical ⇒ μ = 0
[figure]
∵ in NH3 the N–H moments and the lone-pair moment point the same way (add); in NF3 the N–F moments oppose it
⇒ μ: NH3 (1.47 D) > NF3 (0.23 D) > CH4 = PF5 (0)
Answer: (3)