The reactivity of Fluorine (F) is due to its high electronegativity. Electronegativity is a measure of the ability of an atom to attract electrons towards itself. Fluorine has the highest electronegativity of all elements, which means it strongly attracts electrons towards itself. This makes it highly reactive, especially with elements that have a low electronegativity, such as metals.
Fluorine's small size also contributes to its reactivity. Smaller atoms generally have higher electronegativities and are more reactive than larger atoms. The availability of D-orbitals in fluorine also contributes to its reactivity. D-orbitals are involved in chemical reactions and can participate in the formation of bonds between atoms.
So, to summarize, the reactivity of Fluorine is due to its high electronegativity, small size, and the availability of D-orbitals. The strong F-F bond is not a factor that directly contributes to the reactivity of Fluorine.