Question

The noble gas that does NOT occur in the atmosphere is:

• A. He
• B. Ra
• C. Ne
• D. Kr

Answer 1

The Correct Option is B

The question asks to identify the noble gas that does not occur in the atmosphere among the given options. Let's analyze each option:

1. He (Helium): Helium is a noble gas that is present in the Earth's atmosphere but in very low concentrations, around 5 parts per million (ppm).
2. Ne (Neon): Neon is another noble gas found in the Earth's atmosphere at approximately 18 ppm.
3. Kr (Krypton): Krypton is present in the atmosphere, albeit in tiny amounts, around 1 ppm.
4. Ra (Radon): Radon is a noble gas; however, it is not typically present in the atmosphere in significant quantities. Radon is primarily generated from the radioactive decay of radium in soil and rocks and is found more commonly indoors or underground rather than in the open atmosphere.

Therefore, among the given options, Radon (Ra) is the noble gas that is not commonly found in the atmosphere.

Conclusion: The noble gas that does not occur in the atmosphere is Ra (Radon).