Atomic number 7 and the letter N designate nitrogen as the chemical element. Group 15 of the periodic table, often known as the pnictogens, contains nitrogen as the lightest nonmetal element. It ranks eighth in overall abundance in the Milky Way and the Solar System, making it a common element in the cosmos. Two of the element's atoms combine to create the colorless and odorless diatomic gas N2 at standard temperature and pressure. The most common element that isn't mixed, N2 makes up around 78 percent of the Earth's atmosphere. All living things contain nitrogen, which is mostly found in amino acids (and thus proteins), nucleic acids (DNA and RNA), and the energy-transfer molecule adenosine triphosphate.
