In CO2, how many electron domains around the central atom and what is the molecular geometry?

In CO2, how many electron domains around the central atom and what is the molecular geometry?

• A. 2 electron domains; linear
• B. 3 electron domains; trigonal planar
• C. 4 electron domains; tetrahedral
• D. 5 electron domains; trigonal bipyramidal

Answer: (A)

In CO2, the central carbon has two regions of electron density: one for each C=O bond. In VSEPR theory, each bond or lone pair counts as an electron domain, and there are no lone pairs here. So there are two electron domains, which arrange themselves to minimize repulsion in a straight line. With two domains, the geometry is linear, giving a bond angle of 180 degrees. Remember that multiple bonds count as a single domain for this purpose, so two bonds still yield two domains. If the molecule had three, four, or five domains, you’d get trigonal planar, tetrahedral, or trigonal bipyramidal geometries, respectively, but CO2 only has two domains.

In CO2, the central carbon has two regions of electron density: one for each C=O bond. In VSEPR theory, each bond or lone pair counts as an electron domain, and there are no lone pairs here. So there are two electron domains, which arrange themselves to minimize repulsion in a straight line. With two domains, the geometry is linear, giving a bond angle of 180 degrees. Remember that multiple bonds count as a single domain for this purpose, so two bonds still yield two domains. If the molecule had three, four, or five domains, you’d get trigonal planar, tetrahedral, or trigonal bipyramidal geometries, respectively, but CO2 only has two domains.