The element that does not have the same number of electrons in its outermost shell as the other elements in its group is hydrogen (H).
Hydrogen is in group 1 of the periodic table and has one electron in its outermost shell, but it is often considered a unique case because it is a nonmetal, while the other elements in group 1 (alkali metals) are metals. The other options (bromine, helium, and boron) have their respective group characteristics.