Multiple choice general knowledge science & technology Number of atoms in outer most shell for halogens? 4 7 6 2 Reveal answer Fill a bubble to check yourself B Correct answer Explanation Halogens belong to Group 17 of the periodic table. They have a valence shell configuration of ns^2 np^5, totaling 7 electrons in their outermost shell, making them highly reactive as they seek one more electron to complete an octet.