What happens to the reactivity of alkali metals as you go down Group 1?

As you move down Group 1 in the periodic table, the reactivity of alkali metals increases. This trend is primarily due to the atomic structure of the alkali metals. As you progress down the group, each element has an additional electron shell compared to the one above it. This increased distance between the outermost electron and the nucleus means that the outer electron is less strongly attracted to the positively charged nucleus.

Furthermore, the shielding effect becomes more pronounced as the number of inner electron shells increases. This shielding effect reduces the effective nuclear charge felt by the outermost electron, making it easier for that electron to be lost during chemical reactions. Since alkali metals react by losing their single outer electron to form positive ions, a lower attraction means that these elements become more reactive as you descend the group.

Thus, the increased atomic size and the greater shielding effect coupled with the weaker attraction to the nucleus lead to the conclusion that the reactivity of alkali metals indeed increases down the group.