Which group of elements is more reactive due to lower ionization energy?

The correct answer is the alkali metals, which are known for their high reactivity due to their low ionization energies. Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Alkali metals, found in Group 1 of the periodic table, have only one electron in their outermost shell. This single electron is held relatively loosely because it is far from the positively charged nucleus, resulting in a lower ionization energy compared to other groups.

As the ionization energy decreases, the tendency for the atom to lose that outer electron and form a positive ion increases, making the element more reactive. Alkali metals readily lose their outermost electron during reactions, particularly with nonmetals, to achieve a more stable electronic configuration.

In contrast, other groups like the alkaline earth metals and transition metals have higher ionization energies, which contributes to their lower reactivity relative to alkali metals. Noble gases, on the other hand, have a complete outer shell and are typically very unreactive due to their high ionization energies and stable electronic configurations. Therefore, alkali metals are far more reactive due to their significantly lower ionization energy compared to the other options.