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- Dictionaryno·ble gas/ˌnōb(ə)l ˈɡas/
noun
- 1. any of the gaseous elements helium, neon, argon, krypton, xenon, and radon, occupying Group 0 (18) of the periodic table. They were long believed to be totally unreactive but compounds of xenon, krypton, and radon are now known.
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