Nitrogen is a colorless, odorless gas that makes up about 78% of the Earth's atmosphere. It is a vital element for all living organisms, as it is a key component of amino acids, proteins, and nucleic acids, which are essential for life. Nitrogen is represented by the chemical symbol N and has an atomic number of 7. In nature, nitrogen exists in various forms, including nitrogen gas (N₂) and nitrates, which are important for plant growth. The nitrogen cycle describes how nitrogen moves through the environment, involving processes like nitrogen fixation, where certain bacteria convert atmospheric nitrogen into forms usable by plants.