The primary gas in our atmosphere is nitrogen, which comprises about 78% of the Earth's atmosphere by volume. This is followed by oxygen, which accounts for approximately 21%. Nitrogen is a diatomic molecule (N₂) and is inert, meaning it does not readily react with other chemicals under normal conditions. The presence of nitrogen helps to dilute oxygen and other reactive gases, making our atmosphere stable and conducive to life. Oxygen is crucial for the survival of aerobic organisms, while nitrogen is essential in various biological processes, such as the synthesis of proteins and nucleotides.