NCERT Exercise 4.8 - Chemical Bonding and Molecular Structure
Question: Why is the H-O-H angle in water less than the H-N-H angle in ammonia although both have distorted tetrahedral geometry?
Answer: H2O has two lone pairs whereas NH3 has one. The stronger lone-pair-lone-pair and lone-pair-bond-pair repulsions in H2O compress the angle to about 104.5 degrees, below NH3's about 107 degrees.
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