What is the Reactivity Trend as you go down Group 7? Why is this?

-As you go down the Group, it becomes Less Reactive -This is because a Halogen needs 1 Electron to have a Stable Electronic Structure [Which also forms a -1 Ion] -So as you go down the Group, it becomes Harder to Attract that Electron, because of the large Atomic Radius [Attraction from the Positive Nucleus to the Negative Electron]