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How do double bonds change the shape of an ethene molecule?

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representations of molecular structure — molecule Several methods of representing a molecule's structure. In Lewis structures, element symbols represent atoms, and dots represent electrons surrounding them. A pair of shared electrons (covalent bond) may also be shown as a single dash. The ball-and-stick model better illustrates the spatial arrangement of the atoms. For aromatic compounds, the Kekulé structure is common, in which each bond is represented by a dash, carbon atoms are implied where two or more lines meet, and hydrogen atoms are usually omitted. Bond-line formulas, similar to the Kekulé structure, are often used for complex nonaromatic organic compounds. Sugars are often drawn as Fischer projections, in which the carbon “backbone” is drawn as a straight vertical line, with carbon atoms implied where horizontal lines intersect the vertical one.

In the ethene (or ethylene) molecule, the presence of a double bond fundamentally dictates its geometry through hybridization.

Each carbon atom undergoes $s p^{2}$ hybridization, where one $2 s$ and two $2 p$ orbitals mix to form three hybrid orbitals pointing toward the corners of an equilateral triangle. This results in a planar triangular arrangement around each carbon, with bond angles close to 120°.12

The double bond itself consists of a sigma bond and a pi bond. The pi bond is formed by the overlap of unhybridized $2 p$ orbitals that lie perpendicular to the plane of the triangle. Because this overlap is maximized when the orbitals are parallel, the double bond prevents free rotation around the carbon-carbon axis. This imparts torsional rigidity to the molecule, ensuring that ethene remains a flat, planar structure.314