The most abundant gas in the atmosphere is nitrogen, making up about 78% of the Earth's atmosphere by volume. It is a colorless, odorless gas that plays a crucial role in the biological and chemical processes of life. While nitrogen itself is inert and does not react easily with other substances, it is essential for the synthesis of amino acids, which are the building blocks of proteins. Additionally, nitrogen is a key component of nucleic acids like DNA and RNA, thus playing an important role in genetics and cell function.