Question

The bond angle in ammonia molecule is ____.

• A. \(109^\circ 28'\)
• B. \(107^\circ 48'\)
• C. \(104^\circ 31'\)
• D. \(105^\circ 28'\)

Hint:

Lone pairs reduce bond angle because lone pair repulsion is greater than bond pair repulsion.

Answer 1

The Correct Option is B

Concept:
Ammonia \((NH_3)\) contains:
• Three bond pairs
• One lone pair on nitrogen atom According to VSEPR theory, lone pair electrons repel more strongly than bond pairs. Due to this repulsion, the ideal tetrahedral bond angle decreases slightly.

Step 1: Understanding the shape of ammonia molecule.
The electronic configuration of nitrogen is: \[ 1s^2 2s^2 2p^3 \] Nitrogen forms three covalent bonds with hydrogen atoms and retains one lone pair. Hence, the geometry becomes pyramidal.

Step 2: Determining the bond angle.
The ideal tetrahedral angle is: \[ 109^\circ 28' \] But due to lone pair-bond pair repulsion, the angle decreases. Thus, the bond angle in ammonia becomes: \[ 107^\circ 48' \] Therefore, \[ \boxed{107^\circ 48'} \] is the correct answer. Hence, the correct option is: \[ \boxed{(2)\ 107^\circ 48'} \]