Ques. 1AIPMT 2010 (Prelims)
In which of the following pairs of molecules/ ions, the central atoms have sp2 hybridisation ?
- NO2- and NH3
- BF3 and NO2-
- NH2- and H2O
- BF3 and NH2-
Answer
(2) BF3 and NO2-
Solution
Steric number = number of σ bonds + number of lone pairs on the central atom.
BF3: 3 σ bonds + 0 lone pair = 3 ⇒ sp2
NO2-: 2 σ bonds + 1 lone pair on N = 3 ⇒ sp2
NH3: 3 σ bonds + 1 lone pair = 4 ⇒ sp3
NH2- and H2O: 2 σ bonds + 2 lone pairs = 4 ⇒ sp3
∴ Both central atoms are sp2 in BF3 and NO2-.
Answer: (2)