Describe and explain how the reactivity of the elements changes as you go down group 1

As you go down group 1, the reactivity increases. This is because each element has only one electron in their outer shell, so need to lose this electron in order to react. As you go down group 1, the number of shells increases, so therefore shielding and distance from nucleus increase. This means that the nuclear attraction on the outer electron decreases as you go down the group, so it is easier to lose an electron and therefore react.