Which one of the following noble gas is obtained by radioactive disintegration ?

Options

A. Kr
B. An
C. Rn
D. Xe

Answer

To solve the question "Which one of the following noble gas is obtained by radioactive disintegration?" we can follow these steps:

### Step-by-Step Solution:

1. **Identify Noble Gases**: First, we need to recall the noble gases, which include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn).

2. **Check for Radioactive Noble Gases**: Among these noble gases, we need to identify which one is known to be radioactive. Radon (Rn) is the only noble gas that is radioactive.

3. **Understand the Source of Radon**: Radon is produced through the radioactive decay of heavier elements, specifically radium (Ra) and thorium (Th) minerals.

4. **Write the Decay Reaction**: The decay of radium can be represented as follows:
- Radium (atomic number 88, mass number 226) decays to produce Radon (atomic number 86, mass number 222) and Helium (alpha particle, atomic number 2, mass number 4).
- The reaction can be summarized as:
\[ \text{Ra}_{88}^{226} \rightarrow \text{Rn}_{86}^{222} + \text{He}_{2}^{4} \]

5. **Select the Correct Option**: Based on the above information, we conclude that Radon (Rn) is the noble gas obtained by radioactive disintegration.

### Final Answer:
The noble gas obtained by radioactive disintegration is **Radon (Rn)**.