Question

Why is ethylene planar?

Answer 1

There is no rotation about the axis joining the 2 carbon atoms, therefore ethylene is a planar molecule.

Explanation:

The diagram below shows the bonding of ethylene molecule.

The `p`-orbitals are perpendicular to the plane. All the rest of the `sigma` bonds are on the plane.

The molecule cannot be twisted without breaking the `pi` bond, as the `p`-orbital needs to remain parallel with each other.