Given a molecule with a central atom bonded to three other atoms and a bond angle of approximately 120°, what is the molecular geometry around the central atom?

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

Answer: (B)

Verified step by step guidance

1. Identify the number of atoms bonded to the central atom and the presence of any lone pairs on the central atom. Here, the central atom is bonded to three other atoms, and no lone pairs are mentioned.
2. Recall that the molecular geometry depends on both the number of bonded atoms and lone pairs around the central atom, as predicted by the VSEPR (Valence Shell Electron Pair Repulsion) theory.
3. Recognize that a bond angle of approximately 120° is characteristic of a trigonal planar geometry, which occurs when there are three bonded atoms and no lone pairs on the central atom.
4. Understand that a tetrahedral geometry has bond angles of about 109.5°, bent geometry usually involves lone pairs causing bond angles less than 120°, and linear geometry has bond angles of 180°, so these do not match the given bond angle.
5. Conclude that the molecular geometry around the central atom with three bonded atoms and a bond angle of approximately 120° is trigonal planar.