The primary gas found in the Earth's atmosphere is nitrogen, which makes up about 78% of the atmosphere. Oxygen follows as the second most abundant gas, accounting for about 21%. The remaining 1% includes other gases like argon, carbon dioxide, and trace gases. Nitrogen is crucial for the Earth's ecosystems, as it is a vital building block of amino acids and proteins necessary for life. While nitrogen is relatively inert, it plays essential roles in various biological processes and helps moderate the atmosphere's overall composition. The balance of these gases ensures that life can thrive on our planet.