Draw a dot and cross diagram of a Chlorine molecule showing the outer electrons only.

Chlorine has seven outer electrons. Electrons like to be in pairs. In one Chlorine atom, there are three pairs and one lonely electron which doesn't have a pair. (draw). So two Chlorine atoms form a Chlorine molecule by sharing a pair of lonely electrons. (draw).This is a molecule of Chlorine, Cl2.The bond formed by the sharing of electrons is known a covalent bond.