Inert gas (5)

<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inert gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for argon that I've seen before include "something inert and insubstantial" , "Inert gas, symbol Ar" , "Chemical element" , "Inert gas used in light bulbs" , "Gas, 1% of atmosphere" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inert gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for radon that I've seen before include "Gaseous element, Rn" , "Rare noble gas" , "Radioactive gas, linked to granite" , "Element, symbol Rn" , "Natural gas considered a hazard to health" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inert gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for xenon that I've seen before include "Inert 18" , "Noble element" , "Inert gas, Xe" , "member of nobility?" , "Gas used in bright lamps" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inert gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for neon that I've seen before include "Gaseous element, in advertising sign say" , "Small plant; colour" , "Brightly coloured advertising sign" , "Gas used in fluorescent lamps" , "Gaseous element, in advertising signs, say" .)
(Another definition for idle gossip that I've seen is " Conversation".)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inert gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for krypton that I've seen before include "Noble gas - Superman's birthplace" , "Noble gas, Kr" , "Superman's world and a gas" , "Inert gas used in florescent lights (7)" , "Inert gas (symbol Kr)" .)