Which type of bond is formed when atoms share electrons?

Atoms form a covalent bond when they share electrons. This type of bond occurs typically between nonmetals and involves the sharing of electron pairs in order to achieve a more stable electron configuration, often resembling that of noble gases. By sharing electrons, each atom can fill its outer electron shell, leading to greater stability.

In contrast, ionic bonds involve the transfer of electrons from one atom to another, resulting in the formation of positively and negatively charged ions that are held together by electrostatic forces. Metallic bonds, on the other hand, involve a 'sea of electrons' that are shared among a lattice of metal atoms, allowing for properties such as electrical conductivity and malleability. Hydrogen bonds are weaker attractions between molecules that involve hydrogen atoms, often forming between molecules where hydrogen is covalently bonded to highly electronegative atoms.

Understanding these differences helps clarify why the sharing of electrons uniquely characterizes covalent bonding.