Final answer:
Among the listed options, argon is the noble gas. Noble gases are part of Group 18 and are known for their low reactivity, which allows them to be used in applications that require an inert atmosphere.
Step-by-step explanation:
The element among the options that is a noble gas is argon. Noble gases, which are part of Group 18, are known for being the least reactive of all the elements because they have filled valence shells. The noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These gases are monatomic and, due to their nonreactive nature at room temperature and pressure, have found use in various applications such as providing an inert atmosphere for chemical reactions and in lighting systems.
Specifically, argon, due to its low reactivity, is widely used in industries. It is utilized in welding to create an inert atmosphere and in light bulbs to prevent the oxidation of the filament. Moreover, the red light emission from neon is well-known for its use in neon signs. The discovery of the first chemical compounds containing noble gases in 1962 challenged the assumption that these gases were nonreactive, but they are still significantly less reactive than other elements.