Here's why:
* Electron Configuration: Bromine has 35 electrons. Its electron configuration is [Ar] 3d10 4s2 4p5. This means it has 7 electrons in its outermost shell (valence shell).
* Octet Rule: Atoms tend to gain, lose, or share electrons to achieve a stable configuration with 8 electrons in their outermost shell (the octet rule).
* Ionic Bond Formation: Bromine is one electron short of having a full octet. By gaining one electron, it becomes a bromide ion (Br-) with the stable electron configuration of the noble gas krypton ([Ar] 3d10 4s2 4p6).
Therefore, bromine readily forms a stable ion by accepting an electron to become a negatively charged bromide ion (Br-).
