sp² hybridization

Let’s examine another simple molecule, ethene (C₂H₄) (Figure 1.1 “Ethene”). Each carbon of ethene is bonded to two hydrogens and a carbon. There is also a double bond between the two carbons.

Figure 1.1. Ethene.

Both the unhybridized atomic orbitals of carbon and the sp³ hybridization we just examined do not explain the bonding observed in ethene. In this case, only the 2s and two of the 2p orbitals hybridize to give three new sp² hybridized orbitals capable of forming the three σ bonds of each carbon in ethene (Figure 1.2 “Hybridization of carbon to generate sp² orbitals”).

Figure 1.2. Hybridization of carbon to generate sp² orbitals.

The three hybridized orbitals arrange in a trigonal planar structure with a bond angle of 120^o following VSEPR (Figure 1.3 “A carbon atom’s trigonal planar  sp² hybridized orbitals”).

Figure 1.3. A carbon atom’s trigonal planar  sp² hybridized orbitals.

The unhybridized 2p orbital in both carbons are left available to form the double bond’s π bond.