Chlorine is the most reactive. Iodine is the least reactive. Fluorine is so reactive that it cannot be included since it reacts with those materials that would be used to manufacture the container. Because fluorine is so reactive, it would have ranked at the top of the reactivity list. Astatine and fluorine are left out.
Fluorine is too reactive.
Astatine is a radioactive and mostly man made element. It behaves like iodine.