Final answer:
Noble gases do not react because they have a full outer electron shell, making them chemically stable.
Step-by-step explanation:
Noble gases, such as helium, neon, and argon, do not usually react because they have a full outer shell of electrons. This stability is due to the fact that their outer electron shells are already filled with the maximum number of electrons. Since their outer shells are complete, they neither gain nor lose electrons easily, which makes them unreactive.
Learn more about Chemical reactivity of noble gases