Can bonding molecular orbitals have a node? If so, what does it look like?

When two atomic orbitals overlap, they form two molecular orbitals, of which one is bonding and one is antibonding.

For example, two #p# orbitals overlap to form a #π# (bonding) and a #π#* (antibonding) orbital.

We can see this in ethene, buta-1,3-diene, and benzene.

Ethene

(from www.dlt.ncssm.edu)

Each time you go up an energy level, you get another node.

Buta-1,3-diene

If you use four atomic #p# orbitals to make the molecular orbitals in butadiene, you get four new #π# orbitals.

Each level up has one more node.

The four #p# electrons go into the two bonding orbitals, one of which has a node.

Benzene

The six #p# orbitals in benzene combine to form six #π# orbitals, of which three are bonding and three are antibonding.

(from jwhitesell.ucsd.edu)

The lowest-energy orbital, #π_1#, has zero nodes and has the familiar doughnut shape. It holds two #π# electrons.

#π_2# and #π_3# are degenerate bonding orbitals with one node. The node in #π_2# is at right angles to the node in #π_3#. Each orbital contains two electrons.

#π_4# and #π_5# are degenerate antibonding orbitals with two nodes at right angles to each other.

#π_6# is an antibonding orbital with three nodes.