Which of the following statements is not correct for a noble gas

Options

A. Ar is used in electric bulbs
B. Kr is obtained during radioactive disintegration
C. Half life of Rn is only 3.8 days
D. He is used producing very low temperature

Answer

To determine which statement is not correct for noble gases, we will analyze each statement provided in the question.

### Step 1: Analyze the Statements
1. **Statement 1**: "Argon is used in electric bulbs."
- **Analysis**: This statement is correct. Argon is indeed used in electric bulbs to prevent the filament from oxidizing and prolonging the life of the bulb.

2. **Statement 2**: "Krypton is obtained during radioactive disintegration."
- **Analysis**: This statement is incorrect. Krypton is primarily obtained from the Earth's atmosphere and not as a product of radioactive disintegration. Radon, a noble gas, is the one that is produced during radioactive decay.

3. **Statement 3**: "The half-life of Argon is only 3.8 days."
- **Analysis**: This statement is correct. Argon-39, a radioactive isotope of Argon, has a half-life of about 3.8 days.

4. **Statement 4**: "Helium is used to produce very low temperatures."
- **Analysis**: This statement is correct. Helium is used in cryogenics due to its very low boiling point, making it suitable for producing extremely low temperatures.

### Conclusion
The statement that is not correct for noble gases is **Statement 2**: "Krypton is obtained during radioactive disintegration."