# How do pi bonds work?

##### 1 Answer

Jun 5, 2016

**ORBITAL PERSPECTIVE**

Pi (**atomic orbitals** *sidelong*, as shown below. In contrast, sigma (*head-on*.

Either way, this overlap can either be *in-phase* or *out-of-phase*.

- The
**in-phase**one (same colors overlapping) is**lower**in energy and is called the**bonding**#pi# overlap. It generates a#pi# molecular orbital. - The
**out-of-phase**one (opposite colors overlapping) is**higher**in energy and is called the**antibonding**#pi# overlap. It generates a#pi^"*"# molecular orbital.

A double bond has one#sigma# and one#pi# bond, while a triple bond has one#sigma# and two#pi# bonds.

**MOLECULAR ORBITAL DIAGRAM PERSPECTIVE**

The MO diagram depiction is:

where:

#pi_(npx)# is the**bonding**molecular orbital formed by the in-phase overlap of an#np_x# with an#np_x# atomic orbital.#pi_(npy)# is the**bonding**molecular orbital formed by the in-phase overlap of an#np_y# with an#np_y# atomic orbital.#pi_(npx)^"*"# is the**antibonding**molecular orbital formed by the out-of-phase overlap of an#np_x# with an#np_x# atomic orbital.#pi_(npy)^"*"# is the**antibonding**molecular orbital formed by the out-of-phase overlap of an#np_y# with an#np_y# atomic orbital.

We have three common ways that we can occupy the

- When the
#pi# molecular orbitals are**filled**but the#pi^"*"# ones are**not**, we have a#pi# bond. - When
**both**kinds of molecular orbitals are filled, those electrons are nonbonding and are*lone pairs*. - When
**neither**kind of molecular orbital is filled, there is*no*lone pair*or*bond.

The