# How do pi bonds overlap?

Jul 20, 2018

Two (unhybridized) $p$ orbitals overlap sideways ("lateral-ly") to form a pi ($\pi$) bond.

#### Explanation:

Molecules containing bonds of orders higher than one (i.e., double and triple bonds) contain $\pi$ bonds. For example, each molecule of ethene ${\text{H"_2 "C" = "C" "H}}_{2}$ contains a carbon-carbon $\text{C"="C}$ double bond.

Each neutral carbon atom contains four valence electrons. The atom undergoes a hybridization process that would result in three $s {p}^{2}$ orbitals and one $2 p$ orbital before bonding to another carbon atom of an identical configuration and forming a carbon-carbon double bond.

As seen in the diagram, the $2 p$ orbital that is left half-filled and not hybridized is capable of overlapping with an equally half-filled and unhybridized $2 p$ orbital from another carbon atom.

The two $2 p$ orbitals overlap in parallel ("sideway") to the bonding axis between the two nuclei and the sigma bond from the overlapping of two $s {p}^{2}$ orbitals. Note that each $p$ orbital contains two petal-like electron clouds such that $\text{two}$ regions of high electron density on opposite sides of the bonding axis (shown in blue in the second diagram) makes a single $\pi$ bond.