Which of the following is NOT a noble gas?

Noble Gases (Group 18): These are a group of chemical elements with similar properties. They are all odorless, colorless, monatomic gases with very low chemical reactivity because their outer electron shells are full. The noble gases include Helium ($He$), Neon ($Ne$), Argon ($Ar$), Krypton ($Kr$), Xenon ($Xe$), and Radon ($Rn$).Nitrogen (Group 15): While Nitrogen ($N$) is a gas at room temperature and makes up 78% of Earth's atmosphere, it is highly reactive compared to noble gases and belongs to the "Non-metals" category. It typically exists as a diatomic molecule ($N_2$)