Bromine typically forms a -1 charge in compounds. This is because it is a halogen, and halogens tend to gain one electron to achieve a stable octet configuration.

Here's why:

* Electronic Configuration: Bromine has 7 valence electrons (electrons in its outermost shell).

* Octet Rule: Atoms want to have 8 electrons in their outermost shell for stability (except for hydrogen and helium which want 2).

* Gaining an Electron: Bromine can gain one electron to reach a stable octet configuration, becoming a bromide ion (Br⁻).

This is why you often see bromine forming compounds like NaBr (sodium bromide) or KBr (potassium bromide).