The chemical formula for nitrogen is N. Nitrogen is a chemical element with the symbol N and atomic number 7. It is the lightest pnictogen and the seventh element of the periodic table. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. At standard conditions, nitrogen is a colorless, odorless, tasteless diatomic gas with the formula N2. It is a constituent of Earth's atmosphere, at 78.08% by volume. Nitrogen is necessary for life and is found in amino acids, proteins, nucleic acids, and chlorophyll.