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

The most abundant gas in the Earth's atmosphere is nitrogen, constituting about 78% of the atmosphere's composition. This gas plays a crucial role in the atmospheric system, as it helps to dilute oxygen and carbon dioxide, stabilizing conditions for life on Earth. Nitrogen is a key component of proteins and nucleic acids, essential for living organisms, and it is relatively inert, meaning it does not readily react with other elements, allowing it to persist in the atmosphere without causing immediate changes.

Oxygen, while critical for aerobic life, makes up only about 21% of the atmosphere. Carbon dioxide is present in trace amounts (approximately 0.04%), but it is vital for processes like photosynthesis and regulating Earth's climate. Hydrogen, although the most abundant element in the universe, is found in very small quantities in the Earth's atmosphere due to its low molecular weight, which allows it to escape into space more readily.

Understanding the composition of the atmosphere is essential for studying weather, climate, and life processes on Earth, as well as the interactions between the various gases and their roles in ecological systems.