Question

h
h:n:h
based on the lewis diagram for nh₃ shown above, the h-n-h bond angle is closest to which of the following?
a 60°
b 90°
c 109.5°
d 120°

Explanation:

Step1: Determine the molecular geometry of \( NH_3 \)

The Lewis structure of \( NH_3 \) (ammonia) shows that the nitrogen atom has 3 bonding pairs (with hydrogen atoms) and 1 lone pair of electrons. Using the valence - shell electron - pair repulsion (VSEPR) theory, the electron - pair geometry is tetrahedral (because there are 4 electron groups: 3 bonding and 1 non - bonding), and the molecular geometry is trigonal pyramidal.

Step2: Recall bond angles in related geometries

For a tetrahedral electron - pair geometry (with 4 electron groups), the ideal bond angle for a molecule with no lone pairs (like \( CH_4 \)) is \( 109.5^{\circ} \). In \( NH_3 \), the lone pair of electrons on the nitrogen atom exerts a greater repulsive force than the bonding pairs. This causes the bonding pairs (the H - N - H bonds) to be pushed closer together, but the bond angle is still closest to \( 109.5^{\circ} \) (compared to the other options: \( 60^{\circ} \) is typical of trigonal planar with some distortion or small ring structures, \( 90^{\circ} \) is typical of octahedral or square planar with some distortions, and \( 120^{\circ} \) is typical of trigonal planar geometry).

Answer:

C. \( 109.5^{\circ} \)