Which gas is most abundant in Earth’s atmosphere?

Nitrogen is the most abundant gas in Earth's atmosphere, making up about 78% of the atmosphere by volume. This gas plays a critical role in various atmospheric processes and is essential for life as it is a key component of amino acids and nucleic acids, necessary for building proteins and genetic material in living organisms.

In contrast, oxygen comprises approximately 21% of the atmosphere and is crucial for respiration and combustion processes. While carbon dioxide is an important greenhouse gas and vital for photosynthesis, it exists in much smaller concentrations, roughly 0.04%. Helium, being a noble gas, is present in trace amounts in the atmosphere and is not significant compared to nitrogen or oxygen. Understanding the composition of the atmosphere is vital for studying climate patterns, weather phenomena, and biological processes on Earth.