What gas is classified as non-reactive?

Noble gases are classified as non-reactive because they have a complete outer shell of electrons, which makes them stable and less likely to form chemical bonds with other elements. This stability is a result of their electronic configuration, which prevents them from easily gaining or losing electrons. Consequently, noble gases—such as helium, neon, argon, krypton, xenon, and radon—typically do not participate in chemical reactions under standard conditions, thus earning their reputation as non-reactive gases.

In contrast, other options involve gases that do react with various substances. Oxygen, for example, is highly reactive and participates in various oxidation reactions. Carbon dioxide also engages in chemical reactions, particularly in processes like photosynthesis and respiration. Aromatic hydrocarbons can react with other compounds in chemical reactions as well. Hence, the unique electronic structure of noble gases distinguishes them from the other gases listed, solidifying their classification as non-reactive.