The most abundant gas in the atmosphere of Earth is nitrogen, making up about 78% of the atmosphere by volume. Nitrogen is an inert gas, meaning it does not readily react with other elements or compounds in its molecular form (N2). This property allows it to exist in large quantities without significantly contributing to chemical reactions that affect air quality or climate stability. It serves as an essential component of proteins and nucleic acids in living organisms. While nitrogen is vital for life, it is largely unavailable for direct use by most organisms until fixed by certain bacteria through the nitrogen cycle.