Why do alkali metals rank high in the reactivity series?

Alkali metals rank high in the reactivity series due to their single electron in the outermost shell.

Alkali metals, found in Group 1 of the Periodic Table, are known for their high reactivity. This is primarily due to their electronic configuration. They have one electron in their outermost shell, which is loosely held due to the distance from the nucleus. This makes it easy for alkali metals to lose this electron and achieve a stable electronic configuration, thereby making them highly reactive.

The reactivity of alkali metals increases down the group. This is because as we move down the group, the atomic size increases. This increase in atomic size means the outermost electron is further away from the nucleus and is less attracted to the nucleus due to the shielding effect of the inner shell electrons. As a result, the outermost electron can be lost more easily, increasing the reactivity of the alkali metal.

For example, lithium (Li), at the top of Group 1, is less reactive than sodium (Na), which is less reactive than potassium (K), and so on. This trend continues down the group, with francium (Fr) being the most reactive of the alkali metals.

In summary, the high reactivity of alkali metals is a result of their single electron in the outermost shell, which is easily lost in a reaction. This characteristic, combined with the increasing atomic size and shielding effect down the group, results in alkali metals ranking high in the reactivity series.