What is the most abundant gas in the Earth's atmosphere?

The most abundant gas in the Earth's atmosphere is nitrogen, which makes up about 78% of the atmosphere. This high concentration is crucial for various reasons, including its role in the nitrogen cycle, which is essential for the growth of plants and the overall health of ecosystems. Nitrogen itself is inert and does not react easily with other substances, allowing it to dominate the atmosphere without contributing to processes like combustion, which are driven by more reactive gases.

Oxygen, while vital for life as it is necessary for respiration in many organisms, constitutes only about 21% of the atmosphere. Carbon dioxide and hydrogen are present in much smaller quantities, with carbon dioxide being important for processes like photosynthesis but only making up about 0.04% of the atmosphere. Hydrogen, being the lightest element, is also rare in the atmosphere.

This knowledge of atmospheric composition is fundamental when studying environmental science, ecology, and even weather phenomena and climate change. Understanding that nitrogen is the predominant gas shapes our understanding of air quality, pollution, and various biological cycles that sustain life on Earth.