What is the bond angle in a BF_3 molecule?

• A. 120^ext{o}
• B. 109.5^ext{o}
• C. 104.5^ext{o}
• D. 90^ext{o}

Answer: (A)

Verified step by step guidance

1. Identify the central atom in the BF_3 molecule, which is boron (B), and note that it is bonded to three fluorine (F) atoms.
2. Determine the electron domain geometry around the boron atom by counting the number of bonding pairs and lone pairs. In BF_3, boron has three bonding pairs and no lone pairs.
3. Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry. With three bonding pairs and no lone pairs, the electron domains arrange themselves to minimize repulsion, resulting in a trigonal planar shape.
4. Recall that in a trigonal planar geometry, the bond angles between the atoms are all equal and are approximately 120 degrees.
5. Conclude that the bond angle in BF_3 is 120^\text{o} due to its trigonal planar molecular geometry.