Question

what is the bond angle around the indicated trigonal pyramidal atom? <109.5° 120° <120° 109.5°

Explanation:

Step1: Recall VSEPR theory

VSEPR (Valence - Shell Electron - Pair Repulsion) theory is used to predict molecular geometries. For a trigonal pyramidal structure, the central atom has four electron - pair domains (three bonding pairs and one lone pair).

Step2: Consider electron - pair repulsion

The ideal bond angle for a tetrahedral electron - pair geometry (four electron - pair domains) is \(109.5^{\circ}\). But in a trigonal pyramidal geometry (due to the presence of a lone pair which repels bonding pairs more strongly than bonding - bonding pair repulsions), the bond angle is less than \(109.5^{\circ}\).

Answer:

\(< 109.5^{\circ}\)