Question

what is the closest bond angle around the central atom? 180° 120° 90° 109.5°

Explanation:

Step1: Determine the electron - pair geometry

The central atom is oxygen (\(O\)) in \(H_2O\). Oxygen has 6 valence electrons. It forms 2 bonds with hydrogen atoms and has 2 lone pairs. The electron - pair geometry is tetrahedral.

Step2: Consider the effect of lone pairs on bond angle

In a tetrahedral electron - pair geometry, the ideal bond angle is \(109.5^{\circ}\). But due to the repulsion between lone pairs (which is stronger than bond - pair repulsion), the bond angle in \(H_2O\) is slightly less than \(109.5^{\circ}\), but among the given options, \(109.5^{\circ}\) is the closest to the actual bond angle of \(H_2O\) (actual bond angle is approximately \(104.5^{\circ}\)).

Answer:

\(109.5^{\circ}\)