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 has 1 electron in its outermost shell, while the other elements mentioned (boron, helium, bromine) have different electron configurations that characterize their respective groups. Specifically, boron is in group 13, and can have 3 valence electrons, helium is a noble gas with 2 valence electrons, and bromine (group 17) typically has 7 valence electrons. Thus, hydrogen is unique in this context.
47 answers