Which electron geometry corresponds to a molecule with the general formula AX3?

• A. Tetrahedral
• B. Trigonal bipyramidal
• C. Linear
• D. Trigonal planar

Answer: (D)

Verified step by step guidance

1. Identify the meaning of the general formula AX3, where 'A' is the central atom and 'X' represents the atoms bonded to 'A'. This means the central atom is bonded to three other atoms.
2. Recall that electron geometry depends on the number of regions of electron density (bonding and lone pairs) around the central atom. For AX3, consider if there are any lone pairs on the central atom.
3. If there are no lone pairs on the central atom, the three bonded atoms will arrange themselves to minimize repulsion, resulting in a trigonal planar electron geometry with bond angles of approximately 120°.
4. If there were lone pairs, the electron geometry might differ (e.g., tetrahedral if there is one lone pair, or trigonal pyramidal if there are three bonded atoms and one lone pair), but since the problem states AX3 without lone pairs, trigonal planar is correct.
5. Compare the given options: tetrahedral (4 regions of electron density), trigonal bipyramidal (5 regions), linear (2 regions), and trigonal planar (3 regions). Since AX3 corresponds to 3 bonded atoms and no lone pairs, the electron geometry is trigonal planar.