Describe and explain why reactivity increases down Group 1.

Reactivity in Group 1, the alkali metals, increases down the group due to the increasing atomic size and the decreasing attraction between the outer electron and the nucleus. As you move down the group, each element has an additional electron shell, which places the outer electron further from the nucleus. This increased distance reduces the electrostatic force of attraction, making it easier for the outer electron to be lost during reactions. Consequently, elements like potassium are more reactive than lithium, as they can lose their outer electron more readily.