In the first step, the pi bond of the alkene attacks the halogen.

The use of the p-orbitals forms a pi bond.

The molecule can be described as having two pi bonds but without a sigma bond.

Each degree either equals one ring structure or pi bond.

Two pi bonds are the maximum that can exist between a given pair of atoms.

In fact, a 90 twist requires an energy approximately equal to half the strength of a pi bond.

A striking example of this are the pi bonds in benzene.

This is different from a pi bond where they touch sideways.

The result is formation of one sigma bond and two pi bonds.

The other is more loosely held in a pi bond.