Bond formation in chlorine molecule. Illustration of the sharing of electrons (dots and crosses) between two chlorine atoms (Cl) to form a molecule of chlorine (Cl2). This is an example of covalent bonding, with the single bond formed by a shared electron pair consisting of an electron from each atom. The outer electron shell of each atom is shown as a red ring. Chlorine is a gas at room temperature and pressure. For the atoms before the bonds form, see image C028/6472.