Which family in the periodic table is characterized as the least reactive?

The correct answer is the noble gases, which are known for being the least reactive elements in the periodic table. This lack of reactivity is primarily due to their full valence electron shell, which means they do not easily gain or lose electrons to form chemical bonds. This stability makes noble gases, such as helium, neon, and argon, very unreactive under standard conditions.

In contrast, other families in the periodic table display different levels of reactivity. Alkali metals are highly reactive, especially with water and halogens, due to their single electron in the outermost shell, which they readily lose to become more stable. Halogens are also quite reactive, as they have seven electrons in their outer shell and need only one more to achieve a full shell, making them eager to react with other elements. Transition metals exhibit varied reactivity, but on average, they are more reactive than noble gases while also commonly forming complex compounds.

Thus, the unique electronic configuration of noble gases is what sets them apart, allowing them to remain inert and largely unaffected by reactions that other elements frequently participate in.