What is the primary feature of noble gases regarding their reactivity?

Noble gases are characterized by their nonreactivity, primarily due to their full valence shell of electrons. This complete outer electron configuration makes them thermodynamically stable, meaning they have little to no tendency to gain, lose, or share electrons with other elements during chemical reactions. As a result, noble gases do not readily form chemical bonds or engage in reactions with other elements, which is why they are often found in nature as monatomic gases.

The stability provided by a full valence shell is also why noble gases are used in applications where a nonreactive atmosphere is preferred, such as in neon signs or as inert gas environments for sensitive reactions. Their lack of reactivity stands in contrast to many other elements, which seek to attain a full outer shell by participating in chemical bonding.