How are the atoms arranged around the double bond in ethene?

In the ethene (also known as ethylene) molecule, the six atoms involved in the double bond lie in a single plane.12

The arrangement around each carbon atom is as follows:

• Planar Geometry: Each carbon atom is bonded to two hydrogen atoms and one other carbon atom. These three bonding regions adopt a planar triangular arrangement, with bond angles (H–C–H and H–C=C) predicted to be close to 120°.2
• Hybridization: This structure is explained by $s{p}^2$ hybridization, where one $2s$ and two $2p$ orbitals of each carbon atom mix to form three hybrid orbitals pointing toward the corners of an equilateral triangle.3
• Bonding: The three $s{p}^2$ hybrid orbitals form $\sigma$ (sigma) bonds with the two hydrogen atoms and the other carbon atom. The remaining unhybridized $2p$ orbital on each carbon lies perpendicular to this plane, overlapping side-by-side to form a $\pi$ (pi) bond.3

This planar configuration confers torsional rigidity to the molecule, as twisting the structure would reduce the overlap of the $2p$ orbitals and weaken the $\pi$ bond.3