Which of the following noble gases is commonly found in the atmosphere?

Analysis

The question asks for the noble gas that is most abundant and commonly found in the Earth's atmosphere.

Concept

Noble gases (Group 18 elements) are chemically inert due to their stable octet configuration. While they are all present in the atmosphere in trace amounts, their concentrations vary significantly:

• Argon (Ar): Makes up approximately 0.93% of the Earth's atmosphere by volume. It is the third most abundant gas in the atmosphere after Nitrogen and Oxygen.
• Neon (Ne): Present in very small trace amounts (approx. 0.0018%).
• Helium (He): Present in even smaller trace amounts (approx. 0.0005%).
• Xenon (Xe): Present in extremely minute trace amounts (approx. 0.000008%).

Solution

1. Identify the composition of air: The atmosphere is primarily composed of Nitrogen (~78%) and Oxygen (~21%).
2. Locate the noble gases: Among the noble gases, Argon is the only one present in a significant percentage (nearly 1%).
3. Evaluate the options: Because Argon constitutes nearly 1% of the air we breathe, it is the most "common" noble gas found in the atmosphere. The others are present in such small quantities that they are considered rare gases.

Conclusion

Based on the atmospheric composition, Argon is the most abundant noble gas in the atmosphere.

Exam Tip: Remember the acronym "N-O-A" for the most abundant gases in the atmosphere: Nitrogen, Oxygen, and Argon. This will help you quickly identify Argon as the most common noble gas in any exam setting.