Here's why:

* Chlorine atoms have 7 electrons in their outermost shell. They need one more electron to achieve a stable octet configuration.

* In chlorine gas (Cl₂) two chlorine atoms share one electron each, forming a covalent bond.

* This sharing of electrons results in a neutral molecule because each chlorine atom effectively has a full octet of electrons.

Let me know if you have any other chemistry questions!