Radon
/rˈeɪˌdɑn/
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Definition
(noun) The chemical element (symbol Rn, formerly Ro) with atomic number 86. It is an odorless, colorless, chemically inert but radioactive noble gas.
Sentence Examples
Helium, neon, argon, krypton, xenon and radon are noble gases.
Several measurements show high radon levels in this area.
CEFR Practice Quiz
The homeowner installed a ventilation system to reduce the levels of ____ gas in the basement.