Chapter 2 - Atoms, Molecules, and Ions - Exercises - Page 77: 2.58d

Charge: -1

Atoms of elements want to have the electron configuration of the nearest noble gas (in terms of number of electrons) on the periodic table. The nearest noble gas to Bromine (Br) is Krypton. In order to gain the electron configuration of Krypton, a Bromine atom must gain an electron, making the most common charge of a Bromine ion -1.