Key Concepts and Summary
Covalent bonds form when electrons are shared between atoms and are attracted by the nuclei of both atoms. In pure covalent bonds, the electrons are shared equally. In polar covalent bonds, the electrons are shared unequally, as one atom exerts a stronger force of attraction on the electrons than the other. The ability of an atom to attract a pair of electrons in a chemical bond is called its electronegativity.
The difference in electronegativity between two atoms determines how polar a bond will be. In a diatomic molecule with two identical atoms, there is no difference in electronegativity, so the bond is nonpolar or pure covalent. When the electronegativity difference is very large, as is the case between metals and nonmetals, the bonding is characterized as ionic.
distance between the nuclei of two bonded atoms at which the lowest potential energy is achieved
bond formed when electrons are shared between atoms
tendency of an atom to attract electrons in a bond to itself
polar covalent bond
covalent bond between atoms of different electronegativities; a covalent bond with a positive end and a negative end
pure covalent bond
(also, nonpolar covalent bond) covalent bond between atoms of identical electronegativities