Question

Which one of the following noble gas is not found in the atmosphere ?

• A. $Rn$
• B. $Kr$
• C. $Ne$
• D. $Ar$

Answer 1

The correct option is A $Rn$

Except Radon, All noble gases occur​ in the atmosphere. Rn is a radioactive element obtained by the disintegration of radium.
${}_{88}R{a}^{226}{\to }_{86}R{n}^{222}{+}_{2}H{e}^4$