Question

Which of the following is a radioactive noble gas?

• A. He
• B. Ne
• C. Xe
• D. Rn

Hint:

Radon is the only naturally occurring radioactive noble gas commonly discussed at school level.

Answer 1

The Correct Option is D

Step 1: Fact check.
Among noble gases, radon (Rn) is naturally radioactive (formed in the decay chain of $^{238}$U and $^{232}$Th).
Step 2: Eliminate others.
He, Ne, and Xe are stable (non-radioactive) isotopes under normal conditions.
Step 3: Conclusion.
Therefore, the radioactive noble gas is Rn.