why does the reactivity of elements increase going down Group 1 from lithium to rubidium but decreases going down Group 7 from fluorine to iodine?

     The reactivity of group 7 elements decreases down the group because, as you go down the group: The atoms get larger. The outer shell gets further from the nucleus. The attraction between the nucleus and electrons gets weaker, so an electron is less easily gained.

Explanation:

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