kovalent

Kovalent, often rendered in English as covalent, refers to a type of chemical bond formed by sharing electron pairs between atoms. In a covalent bond, each participating atom contributes one or more electrons to a shared pair, allowing the atoms to approach noble-gas electron configurations. Covalent bonds typically form between nonmetal elements with similar electronegativities, though the bond character ranges from nonpolar to polar covalent, and can acquire ionic character as electronegativity differences increase.

Bonding can be single, double, or triple, corresponding to one, two, or three shared electron pairs. Higher bond order generally shortens the bond and strengthens it. The polarity of a covalent bond depends on electronegativity differences: nonpolar covalent bonds occur when atoms share electrons more or less equally, while polar covalent bonds create partial charges, as seen in water (O–H).

Covalent compounds may consist of discrete molecules (for example H2, CH4, H2O) or form extended networks (for example diamond, quartz, silicon dioxide) where atoms are linked in a continuous covalent lattice.

Properties vary widely: molecular covalent substances often have lower melting and boiling points and are poor electrical conductors, while network covalent solids are typically very hard and have very high melting points. Biochemistry and organic chemistry rely on covalent bonds to build the macromolecules of life, and covalent chemistry underlies many materials, catalysts, and polymers.

Historically, the concept emerged from Lewis structures and was refined by quantum theory and electronegativity scales developed in the 20th century.