Britannica Sources used in this answer

What kinds of bonds make up a double bond?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram showing the formation of a polar covalent bond in a water molecule, with two hydrogen atoms bonding to one oxygen atom to form H2O, illustrating shared electrons and chemical reaction. — covalent bond In polar covalent bonds, such as that between hydrogen and oxygen atoms, the electrons are not transferred from one atom to the other as they are in an ionic bond. Instead, some outer electrons merely spend more time in the vicinity of the other atom. The effect of this orbital distortion is to induce regional net charges that hold the atoms together, such as in water molecules.

A double bond is a type of covalent bond in which two atoms share two pairs of electrons, totaling four electrons.12

In terms of chemical bonding theory, a double bond is composed of two distinct types of bonds:

One sigma bond ( $σ$ ): This bond is formed by the head-to-head overlap of orbitals, resulting in an electron distribution that is cylindrically symmetrical about the internuclear axis.3
One pi bond ( $π$ ): This bond is formed by the side-to-side overlap of orbitals, typically unhybridized p orbitals, which lie perpendicular to the internuclear axis.43

The combination of these two bonds makes double bonds stronger and shorter than single bonds. Additionally, the presence of the pi bond restricts free rotation around the bond axis, which imparts torsional rigidity to the molecule.124