For a molecule with the formula AB3 and no lone pairs on the central atom, what are the electron geometry and molecular geometry of the molecule?

• A. Electron geometry: trigonal bipyramidal; Molecular geometry: T-shaped
• B. Electron geometry: linear; Molecular geometry: linear
• C. Electron geometry: trigonal planar; Molecular geometry: trigonal planar
• D. Electron geometry: tetrahedral; Molecular geometry: trigonal pyramidal

Answer: (C)

Verified step by step guidance

1. Identify the total number of regions of electron density (bonding and lone pairs) around the central atom in the molecule AB3. Since there are no lone pairs on the central atom, all regions correspond to bonding pairs.
2. Recall that the electron geometry depends on the total number of electron regions around the central atom. For 3 bonding pairs and 0 lone pairs, the electron geometry is trigonal planar.
3. Understand that molecular geometry describes the arrangement of only the atoms (not lone pairs) in the molecule. Since there are no lone pairs, the molecular geometry is the same as the electron geometry.
4. Therefore, for AB3 with no lone pairs, both the electron geometry and molecular geometry are trigonal planar.
5. Review the other options and recognize that geometries like trigonal bipyramidal or tetrahedral require more than 3 regions of electron density, and linear geometry corresponds to 2 regions, so they do not apply here.