Which type of bond forms when atoms differ in electronegativity?

An ionic bond forms when there is a significant difference in electronegativity between two atoms, typically involving a metal and a non-metal. In this scenario, one atom will have a much greater tendency to attract electrons than the other. As a result, the atom with the higher electronegativity will attract one or more electrons from the other atom, leading to the formation of ions. The atom that loses one or more electrons becomes a positively charged ion (cation), while the atom that gains electrons becomes a negatively charged ion (anion). The electrostatic attraction between these oppositely charged ions results in the formation of an ionic bond.

This type of bonding is contrasted with covalent bonds, where two atoms share electrons equally or nearly equally, which usually occurs between atoms with similar electronegativities. Hydrogen bonds are a specific type of dipole-dipole attraction that occurs between hydrogen and highly electronegative atoms like oxygen or nitrogen, and metallic bonds involve a 'sea of electrons' that are delocalized over a lattice of metal cations. These distinctions clarify why the formation of an ionic bond is specifically related to significant differences in electronegativity.