Covalent bond: definition in chemistry
Covalent bond: A chemical bond in which two atoms share one or more pairs of electrons. It usually forms between nonmetal atoms.
Each shared pair of electrons is attracted to both nuclei, which holds the atoms together. Atoms can share one pair (a single bond), two pairs (a double bond) or three pairs (a triple bond), and multiple bonds are shorter and stronger. When the two atoms have different electronegativities, the electrons are shared unequally and the bond is polar.
Examples
- H₂ — two hydrogen atoms share one pair of electrons
- O₂ — two oxygen atoms joined by a double bond
- N₂ — a triple bond, one of the strongest known
- Diamond — a giant network of carbon–carbon covalent bonds
On the periodic table
Covalent bonds form mainly between nonmetals at the upper right of the table, whose similar electronegativities make sharing electrons easier than transferring them.