Which elements are known for their stability, having eight valence electrons?

The correct answer highlights the noble gases, which are elements characterized by having a complete set of eight valence electrons in their outer electron shell. This stable electron configuration typically results in very low reactivity, as they have little tendency to lose, gain, or share electrons with other elements. Examples of noble gases include helium, neon, argon, krypton, xenon, and radon.

In contrast, alkali metals have only one valence electron, making them highly reactive as they seek to lose that electron to achieve a more stable electron configuration. Halogens, on the other hand, have seven valence electrons and are also quite reactive since they are only one electron short of achieving stability, leading them to readily gain or share an electron. Transition metals feature variable valence electrons and do not inherently possess the same stable octet configuration seen in noble gases, which contributes to their complex chemistry and reactivity. Therefore, noble gases are uniquely recognized for their stable configuration of eight valence electrons.