Why does the reactivity of alkali metals increase down the group?

The reactivity of alkali metals increases down the group due to the increasing ease of losing the outermost electron.

In the periodic table, alkali metals are found in Group 1. They include lithium, sodium, potassium, rubidium, caesium, and francium. These metals are known for their high reactivity, which increases as you move down the group. This trend is due to the atomic structure of alkali metals and how easily they can lose their outermost electron to achieve a stable electron configuration.

Alkali metals have one electron in their outermost energy level, which is far from the positive charge of the nucleus. As you move down the group, the outermost electron is held less tightly to the nucleus because the distance between them increases. This is due to the addition of energy levels. The increased distance reduces the attractive force between the nucleus and the outermost electron, making it easier for the electron to be lost in a chemical reaction.

Furthermore, the increase in atomic radius down the group also results in a decrease in ionisation energy. Ionisation energy is the energy required to remove an electron from an atom. The lower the ionisation energy, the easier it is for an atom to lose an electron and hence, the more reactive the atom is. As you move down the group, the ionisation energy decreases, making the alkali metals more reactive.

In summary, the reactivity of alkali metals increases down the group because the outermost electron is less tightly held by the nucleus and can be lost more easily in a chemical reaction. This is due to the increasing atomic radius and decreasing ionisation energy as you move down the group.