Which of the following is a property of noble gases?

Noble gases are characterized by their chemical inertness, which is primarily due to their full valence electron shells. This stable electron configuration means that noble gases do not easily react with other elements, which is why they are known for their lack of reactivity.

In terms of their physical state, noble gases, such as helium, neon, argon, krypton, xenon, and radon, exist as gases under standard temperature and pressure conditions. This aligns with the properties of gases, as they have neither a defined shape nor a defined volume and will expand to fill their containers.

While noble gases are not found as liquids at room temperature, they can be liquefied at low temperatures or under high pressure. They are not classified as metals; rather, they are nonmetals. Therefore, the correct answer reflects that noble gases exist as gases under standard conditions, which is a key property that distinguishes them from other elements in the periodic table.