The chemical element known as the "noble gas" is **argon**, which is one of the elements in Group 18 of the periodic table, also known as the noble gases. Argon is characterized by its lack of reactivity due to its full valence electron shell, making it stable and non-bonding under standard conditions. It constitutes about 0.93% of the Earth's atmosphere and is commonly used in various industrial applications, such as providing an inert atmosphere for welding and in fluorescent lights. Other noble gases include helium, neon, krypton, xenon, and radon, all known for their low chemical reactivity.