BioMedical Admissions Test (BMAT) 2025 – 400 Free Practice Questions to Pass the Exam

As you move down Group VII of the periodic table, which is comprised of the halogens (fluorine, chlorine, bromine, iodine, and astatine), the reactivity of the elements decreases. This is fundamentally linked to the atomic structure of the elements within this group.

Reactivity in Group VII is primarily related to the ability of the halogens to attract and gain electrons to achieve a stable electronic configuration, typically a full outer shell. As you descend the group, the atoms become larger due to the addition of electron shells. The increasing distance between the nucleus and the outermost electrons reduces the nucleus's effective pull on incoming electrons. Additionally, the presence of inner electron shells causes increased electron shielding, which further diminishes the attraction between the nucleus and the outermost electron shell.

Consequently, while the halogens are all reactive nonmetals, they do not react as vigorously as you move from fluorine down to astatine. Thus, the trend observed is a decrease in reactivity down the group. Understanding this concept is crucial for predicting and explaining the chemical behavior of halogens and how they participate in reactions.