What is the primary component of Earth's atmosphere?

The primary component of Earth's atmosphere is nitrogen, which makes up about 78% of the atmosphere by volume. This gas plays a crucial role in various atmospheric processes and is inert, meaning it does not easily react with other substances. Nitrogen is essential for life, as it is a key component of amino acids and nucleic acids, but it is not utilized directly by most organisms in its gaseous form. Instead, nitrogen must undergo a process called nitrogen fixation to be converted into usable forms, such as nitrates.

While oxygen is vital for life and constitutes about 21% of the atmosphere, it is not the predominant gas. Carbon dioxide and argon make up much smaller percentages, with carbon dioxide being essential for photosynthesis but only around 0.04% of the atmosphere, and argon being a noble gas present at about 0.93%. Therefore, the significance of nitrogen as the primary component is evident in its abundance and role in the atmosphere's stability and functionality.