In the context of atmospheric composition, which gas comprises the smallest percentage?

The gas that comprises the smallest percentage in the Earth's atmosphere is argon. Argon makes up about 0.93% of the atmosphere, which is significantly less than nitrogen and oxygen, which account for approximately 78% and 21%, respectively. Carbon dioxide is present in even smaller quantities, around 0.04%, but argon still surpasses it in overall atmospheric composition.

Understanding the composition of the atmosphere is crucial in physical geography as it influences climate, weather patterns, and the availability of essential gases for life. While nitrogen, oxygen, and carbon dioxide play vital roles in ecological and biological processes, argon is largely inert and does not react chemically under typical atmospheric conditions. This distinct characteristic of argon, along with its low percentage, highlights why it is identified as the gas comprising the smallest portion of the atmosphere.