Explain why the reactivity of the elements in group 1 increases as we go down the periodic table?

The reactivity of group 1 metals increases as we go down the periodic table because as we go down the group the electrons are further away from the nulceus as the number of shells increase and therefore the attraction the electron feels from the nucleus decreases due to the nucleus being more shielded by the increasing number of shells. As a result the electron in the outer shell is more easily lost to attain isoelectronic configuration, a stable state. This ease og loss of electron leads to an increase in reactivity.