kovalente

Covalent bonds are chemical bonds formed when atoms share one or more pairs of electrons. The shared electrons count toward both nuclei, helping each atom attain a more stable electron configuration, typically resembling the noble gases. Covalent bonding usually occurs between nonmetals with similar electronegativities. In some languages, this bonding is called kovalente.

Bonding can be nonpolar or polar. If the electronegativity difference is small, the electrons are shared nearly equally, yielding a nonpolar covalent bond. A larger difference produces a polar covalent bond with partial charges on the atoms. Very large differences can lead to ionic bonds, while covalent or coordinate (dative) bonds involve sharing in which both electrons come from one atom.

Bond order, length, and strength vary with the atoms involved. Single bonds are generally longer and weaker than double bonds, which are shorter and stronger, while triple bonds are the shortest and strongest. Classic examples include H2 (nonpolar, single), O2 (double), and N2 (triple).

Theoretical descriptions include valence bond theory, which emphasizes localized bonds, and molecular orbital theory, which describes electrons delocalized over the entire molecule. Covalent bonds commonly involve sigma bonds formed by end-to-end overlap and pi bonds from side-to-side overlap; hybridization (sp, sp2, sp3) helps explain molecular geometry, often predicted by VSEPR theory.

Important among covalent compounds are water, methane, carbon dioxide, and many organic molecules. Covalent bonding underpins the structure of polymers, biomolecules, and minerals with network structures such as diamond or silicon carbide.