VSEPR Theory Predicts Bond Angles from Electron Geometry

Steps:

• Apply VSEPR to count electron domains: bonding and lone pairs determine geometry.
• BF3 has 3 bonding pairs, 0 lone pairs on B (AX3): trigonal planar, 120° angles.
• CH3+ has 3 bonding pairs, 0 lone pairs on C (AX3): trigonal planar, 120° angles.
• NH4+ has 4 bonding pairs, 0 lone pairs on N (AX4): tetrahedral, 109.5° angles.
• Identify option listing both BF3 and CH3+ as having 120° angles.

Why D is correct:

• D selects BF3 and CH3+, both AX3 types with trigonal planar geometry and 120° bond angles per VSEPR.

Why the others are wrong:

• A: Lists only BF3; incomplete, as CH3+ also has 120°.
• B: Lists only CH3+; incomplete, as BF3 also has 120°.
• C: NH4+ is AX4, tetrahedral with 109.5° angles, not 120°.

Final answer: D