Which of the following best describes the effect of having 1 or 2 lone pairs of electrons on the central atom in a molecule?

• A. Always results in a tetrahedral molecular geometry
• B. Formation of a linear molecular geometry
• C. No change in the molecular geometry compared to molecules with no lone pairs
• D. A deviation from ideal bond angles due to increased electron repulsion

Answer: (D)

Verified step by step guidance

1. Recall that the molecular geometry is determined by the arrangement of both bonding pairs and lone pairs of electrons around the central atom, according to the VSEPR (Valence Shell Electron Pair Repulsion) theory.
2. Understand that lone pairs occupy more space than bonding pairs because lone pairs are localized closer to the central atom and repel other electron pairs more strongly.
3. Recognize that the presence of 1 or 2 lone pairs on the central atom causes deviations from ideal bond angles, as lone pairs push bonding pairs closer together, altering the molecular geometry from the idealized shape.
4. Note that this deviation means the molecular geometry is not always tetrahedral when lone pairs are present; instead, the shape adjusts to minimize repulsions, often resulting in geometries like trigonal pyramidal or bent shapes.
5. Conclude that the best description is that lone pairs cause a deviation from ideal bond angles due to increased electron repulsion, affecting the molecular geometry accordingly.