Nitrogen is the fifth most abundant element in the Universe, and 99.64 percent of this elemental nitrogen is the stable isotope nitrogen-14. The second stable isotope, nitrogen-15, is rare in nature; but, it is used extensively in agriculture and industry. All other isotopes of nitrogen are radioactive.
Nitrogen is unique in that it is one of only five stable elements which have an odd number of both protons and neutrons. The other four elements that share this trait are hydrogen, lithium, boron and tantalum.Learn more about Atoms & Molecules