Question

what is the closest bond angle around the central atom in the beh2 molecule? 90° 120° 180° 109.5°

Explanation:

Step1: Determine the electron - pair geometry

The central atom is Be. The number of valence electrons of Be is 2. Each H atom contributes 1 electron. The total number of valence electrons in \(BeH_2\) is \(2 + 2\times1=4\). The number of electron - pairs around Be is \(\frac{4}{2} = 2\) (using the formula \(\text{Number of electron - pairs}=\frac{\text{Total valence electrons}}{2}\) for binary compounds).
When the number of electron - pairs around the central atom is 2, the electron - pair geometry is linear.

Step2: Determine the bond angle

For a linear electron - pair geometry (no lone pairs on the central atom, since all 2 electron - pairs are bonding pairs in \(BeH_2\)), the bond angle is \(180^{\circ}\).

Answer:

\(180^{\circ}\)