What is formed when two atoms share one or more pairs of electrons?

When two atoms share one or more pairs of electrons, a covalent bond is formed. This type of bond occurs when atoms have similar electronegativities, allowing them to share electrons equally or unequally. The shared electrons allow the atoms to achieve a more stable electron configuration, mimicking that of noble gases, which have complete valence shells.

Covalent bonding is common in many molecules, including water (H2O) and carbon dioxide (CO2). The characteristics of covalent bonds often lead to the creation of distinct molecular shapes and properties, which are essential in understanding chemical reactivity and interactions in biological and physical contexts.

In contrast, ionic bonds involve the transfer of electrons from one atom to another, resulting in charged ions that attract each other. Hydrogen bonds are a weaker interaction that occurs between molecules containing hydrogen and electronegative atoms, while Van der Waals forces are weak attractions between molecules or parts of molecules due to transient local partial charges. These distinctions highlight why the formation based on electron sharing specifically defines a covalent bond.