Here's why:
* Octet Rule: Atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their outermost shell (valence shell). This is known as the octet rule.
* Chlorine's Electron Configuration: Chlorine has 17 electrons, with the configuration 2-8-7. This means it has 7 electrons in its outermost shell.
* Gaining an Electron: By gaining one electron, chlorine's valence shell will become 2-8-8, fulfilling the octet rule and achieving a stable configuration like the noble gas Argon.
