What is a noble gas?

The noble gases include helium, neon, argon, krypton, xenon, radon, and oganesson in modern periodic tables. Their chemical inactivity was recognized in the late 19th century, with helium first identified in the Sun’s spectrum in 1868 and isolated on Earth later. Because they rarely form compounds, noble gases were once thought to be completely inert. However, chemists have since made compounds of xenon and krypton under special conditions. Their stability makes them useful in lighting, cryogenics, and controlled environments.