Chlorine exists as a diatomic molecule, meaning it naturally forms a molecule composed of two chlorine atoms bonded together. This is because chlorine atoms are highly reactive and unstable when alone.

Here's why:

* Electronic Configuration: Chlorine atoms have seven electrons in their outermost shell, making them one electron short of a stable octet configuration.

* Octet Rule: To achieve stability, chlorine atoms tend to share one electron each with another chlorine atom, forming a covalent bond.

* Stability: This sharing results in each chlorine atom effectively having eight electrons in its outermost shell, fulfilling the octet rule and achieving a stable electronic configuration.

Therefore, the formula for chlorine is Cl₂, representing this naturally occurring diatomic molecule.