Fluorine (F) and bromine (Br) are in the same group on the periodic table. How do atoms of these elements compare when they form bonds? Both a fluorine atom and a bromine atom lose one electron, and both atoms become stable. A fluorine atom becomes stable by losing one electron, but a bromine atom cannot become stable by losing only one electron. Both a fluorine atom and a bromine atom gain one electron, and both atoms become stable. A fluorine atom becomes stable by gaining one electron, but a bromine atom cannot become stable by gaining only one electron.