A nitrogen atom is a fundamental building block of matter, represented by the symbol N on the periodic table. It has an atomic number of 7, meaning it contains seven protons in its nucleus. Nitrogen is a non-metal and is essential for life, as it is a key component of amino acids and nucleic acids, which are vital for proteins and DNA. In its natural state, nitrogen exists as a diatomic molecule, N2, making up about 78% of Earth's atmosphere. This colorless and odorless gas is relatively inert, meaning it does not easily react with other elements. Nitrogen plays a crucial role in various biological and chemical processes, including the nitrogen cycle, which is essential for maintaining ecosystem balance.