Does reactivity increase or decrease as you go down group 7?

Reactivity will decrease as you travel down group 7 in the periodic table. Group 7 elements need to gain an electron to become stable as they need 8 electrons in their outer shell. Group 7 elements only contain 7 electrons in their outer shell. This means that due to the radius of the elements increasing as you travel down the group the shielding will increase. This means that it is harder for the electron to be attracted to the positive nucleus the further down the group you go.