When going down group 1 on the periodic table, what happens to reactivity?

As you go down the group:shielding increases as electron numbers increase, this means that the distance between the nucleus and outer electron is further and attraction is weaker between the positive nucleus and the negative electronproton number increases, so nuclear power increases HOWEVER, this is outweighed by shielding effectTherefore, the outer electron is more readily lost due to shielding and reactivity increases as you go down group 1