The element considered a noble gas is helium. Positioned in Group 18 of the periodic table, noble gases are characterized by their full valence electron shells, which make them largely inert and nonreactive under standard conditions. Helium is the second lightest element and is known for its low density and low boiling point. It is most commonly found in natural gas deposits and is often used in balloons, cooling applications, and various scientific experiments due to its unique properties. Other noble gases include neon, argon, krypton, xenon, and radon, each exhibiting similar chemical inactivity.