What is the primary component of Earth's atmosphere?

The primary component of Earth's atmosphere is nitrogen, which constitutes about 78% of the atmosphere by volume. This nitrogen is crucial for various biological and chemical processes, including the nitrogen cycle, which is essential for plant growth and health.

Oxygen, while vital for the respiration of most life forms and making up approximately 21% of the atmosphere, is not the dominant gas. Carbon dioxide, though significant for its role in climate regulation and photosynthesis, constitutes only about 0.04% of the atmosphere. Argon is a noble gas making up about 0.93% of the atmosphere and does not participate in chemical reactions in the same way as nitrogen or oxygen. Thus, nitrogen's prevalence and its importance in sustaining life on Earth support why it is regarded as the primary component of the atmosphere.