What causes covalent bonds to form? Use HCl hydrochloric acid) as an example to explain completely the formation of the covalent bonds.

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability.