Which element has the highest percentage in the Earth's atmosphere?

Nitrogen is the most abundant gas in the Earth's atmosphere, making up about 78% of its composition. This significant presence plays a critical role in various atmospheric processes, including the nitrogen cycle, which is essential for life on Earth. Nitrogen is a key component of proteins and nucleic acids, vital for the growth and reproduction of living organisms.

In contrast, oxygen, while crucial for respiration and combustion, constitutes roughly 21% of the atmosphere. Carbon dioxide, although important for photosynthesis and as a greenhouse gas, is present in only about 0.04%. Argon is even less abundant, comprising about 0.93% of the atmosphere. Thus, nitrogen's dominance in the atmospheric composition reflects its fundamental importance in the biological and chemical processes that sustain life.