What is the typical bond angle for sp2-hybridized carbon?

What is the typical bond angle for sp2-hybridized carbon?

• A. 90°
• B. 109.5°
• C. 120°
• D. 180°

Answer: (C)

The main idea is that bond angles are set by the arrangement of electron domains around an atom. When carbon is sp2-hybridized, it uses three sp2 hybrids to form three sigma bonds that lie in a single plane, giving a trigonal planar arrangement. To minimize repulsion among these three regions, the bonds spread out about 120 degrees apart. The unhybridized p orbital sticks perpendicular to that plane and participates in a pi bond, but it doesn’t change the in-plane bond angles. So the typical bond angle for sp2-hybridized carbon is 120 degrees. This contrasts with 109.5 degrees for sp3 (tetrahedral) and 180 degrees for sp (linear). A 90-degree angle would indicate a different geometry, not the sp2 case.

The main idea is that bond angles are set by the arrangement of electron domains around an atom. When carbon is sp2-hybridized, it uses three sp2 hybrids to form three sigma bonds that lie in a single plane, giving a trigonal planar arrangement. To minimize repulsion among these three regions, the bonds spread out about 120 degrees apart. The unhybridized p orbital sticks perpendicular to that plane and participates in a pi bond, but it doesn’t change the in-plane bond angles. So the typical bond angle for sp2-hybridized carbon is 120 degrees. This contrasts with 109.5 degrees for sp3 (tetrahedral) and 180 degrees for sp (linear). A 90-degree angle would indicate a different geometry, not the sp2 case.