What type of hybridization occurs when carbon forms three bonds?

When carbon forms three bonds, it undergoes sp2 hybridization. This occurs because the carbon atom has four valence electrons and when it forms three sigma bonds with other atoms, one of the s orbitals mixes with two of the p orbitals to create three equivalent hybrid orbitals. This arrangement allows for the formation of three sigma bonds and one unhybridized p orbital, which can participate in pi bonding.

In sp2 hybridization, the geometry around the carbon atom is trigonal planar, resulting in bond angles of approximately 120 degrees. This is typical in molecules such as alkenes where carbon atoms are involved in double bonds, contributing to the overall structure and reactivity of the molecule.

As for the other options, sp hybridization occurs when a carbon atom forms two bonds and has a linear geometry with a 180-degree bond angle. sp3 hybridization involves the mixing of one s and three p orbitals, resulting in four equivalent sp3 hybrid orbitals that form tetrahedral geometries, typical for single-bonded carbon atoms. P hybridization refers to the unhybridized p orbitals that are not involved in bonding, which is not applicable when three bonds are present.