What is the molecular geometry of a molecule with three outer atoms and one lone pair on the central atom?

• A. Trigonal planar
• B. Bent
• C. Tetrahedral
• D. Trigonal pyramidal

Answer: (D)

Verified step by step guidance

1. Identify the total number of electron groups around the central atom. In this case, there are three outer atoms and one lone pair, making a total of four electron groups.
2. Recall that four electron groups around a central atom correspond to a tetrahedral electron geometry, which arranges the groups to minimize repulsion.
3. Consider the effect of the lone pair on the molecular shape. Lone pairs occupy space and repel bonding pairs more strongly, which alters the shape formed by the atoms.
4. Determine the molecular geometry by focusing only on the positions of the atoms (ignoring the lone pair). With three bonded atoms and one lone pair, the shape is trigonal pyramidal.
5. Confirm that the molecular geometry is trigonal pyramidal, which is characterized by a pyramid-like shape with the lone pair at the apex and the three atoms forming the base.