Which of the following Lewis structures represents a molecule that would assume a linear geometry?

• A. BF3: F-B-F with three F atoms bonded to B
• B. CO2: O=C=O
• C. H2O: H-O-H with two lone pairs on O
• D. NH3: H-N-H with a lone pair on N

Answer: (B)

Verified step by step guidance

1. Identify the central atom and the number of atoms bonded to it in each molecule to determine the electron domain geometry using the VSEPR theory.
2. For BF3, boron is the central atom bonded to three fluorine atoms with no lone pairs, which corresponds to a trigonal planar electron geometry and a molecular geometry that is also trigonal planar, not linear.
3. For CO2, carbon is the central atom bonded to two oxygen atoms with no lone pairs on carbon, resulting in two regions of electron density arranged linearly, so the molecular geometry is linear.
4. For H2O, oxygen is the central atom bonded to two hydrogen atoms and has two lone pairs, giving four regions of electron density, which leads to a bent molecular geometry, not linear.
5. For NH3, nitrogen is the central atom bonded to three hydrogen atoms with one lone pair, resulting in a trigonal pyramidal molecular geometry, not linear.