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# Which of the following is the only noble gas not to occur in the free state in the atomosphere, air, in oute space or in natural gases etc.

$\begin{array}{1 1} Radon \\ Argon\\ Xenon \\ Krypton \end{array}$
Can you answer this question?

Radon is usually isolated from the radioactive decay of dissolved radium compounds.
answered Jul 28, 2014