What is the molecular geometry of CO2?

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

Answer: (A)

Linearity is determined by how many regions of electron density surround the central atom and whether any lone pairs are present. In CO2, the carbon has two regions of electron density—the two C=O bonds—and no lone pairs. With two electron domains and no lone pairs, the electron-domain geometry is linear, and the absence of lone pairs means the molecular geometry is also linear. The two oxygen atoms align on opposite sides of the carbon, giving a 180° bond angle. This differs from bent shapes (which require lone pairs), trigonal pyramidal (three bonds plus a lone pair), or tetrahedral (four bond pairs). So the geometry is linear.