Which of the following is the most reactive halogen?

Fluorine is the most reactive halogen due to its small atomic size, high electronegativity (3.98 on the Pauling scale - the highest of all elements), and low F-F bond dissociation energy. Reactivity decreases down the group: F > Cl > Br > I. This extreme reactivity makes fluorine dangerous to handle and capable of reacting with almost any element, including noble gases under certain conditions.