Nitrogen is exist in gas state. It comprises 78.3% of the earth's atmosphere by volume(75.5% by mass). Nitrogen has two stable isotopes.14N and 15N.the lighter isotopes is 272.0 time as abundant as the heaver one, as a result the atomic weight of N is 14.0067. N2 is chemically uncreative at the temperatures and pressures of the hydrosphere, biosphere, and atmosphere. It will combine with other elements only under extreme conditions or when catalyzed by enzymes. N2 has a low solubility in water.