NEETChemistryChemical Bonding and Molecular Structure
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The H-O-H bond angle in water is smaller than the H-N-H bond angle in ammonia. Reason (R): According to VSEPR theory, the repulsion between two lone pairs of electrons is greater than the repulsion between a lone pair and a bond pair. In the light of the above statements, choose the most appropriat
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
In water ( H ₂ O ), the central oxygen atom has 2 bond pairs and 2 lone pairs. In ammonia ( NH ₃ ), the central nitrogen atom has 3 bond pairs and 1 lone pair. According to the postulates of VSEPR theory, the order of repulsion between electron pairs is: lone pair - lone pair > lone pair - bond pair > bond pair - bond pair. Because water has two lone pairs, the strong lone pair - lone pair repulsion compresses the H-O-H bond angle to approximately 104.5^ . Ammonia has only one lone pair, so the lone pair - bond pai