* Electronegativity: Bromine has a relatively high electronegativity (2.96 on the Pauling scale). This means it has a strong attraction for electrons.

* Group 17 (Halogens): Bromine is a halogen, and all halogens have a strong tendency to gain one electron to achieve a stable octet configuration (8 electrons in their outermost shell).

Therefore, when bromine forms bonds, it usually does so by gaining an electron from another atom, resulting in a negative charge.