Difference between cl^- cl2 And 2cl

2Cl => 2 Chlorine ions Cl2 => 1 Chlorine atom As you know, Cl has a valency of 1, so it needs one more atom to complete its valency and achieve stability. It can do this either by forming a covalent bond or ionic bond. When you are talking about Cl2, it means two chlorine atoms have come together to form a covalent bond and now form a stable molecule. But 2Cl means, that both the ions exist separately. Wherever you must have read 2Cl, you would have seen some charge specified... which means these ions will combine with oppositely charged ion(s) to complete their valency.