Which element rarely reacts because it has 8 electrons in its outer shell? A. Bromine
B. Xenon
C. Arsenic
D. Potassium

C. Arsenic

Explanation:

Each period is terminated by a noble gas with a closed valence shell with electronic configuration ns²np⁶. Since noble gases have completely filled orbitals in the valence shell and are very stable, it becomes very difficult to alter their stable arrangement by the addition or removal of electrons. They they exhibit very low chemical reactivity

Noble gas elements are: Neon, Argon, Krypton, Xenon, Radon, Helium (2 electrons in outer shell, stable).

the answer is option a.