A nitrogen atom contains seven protons. This is true of all isotopes of nitrogen; radioactive isotopes of the element vary only in their number of... A nitrogen atom contains seven protons. This is true of all isotopes of nitrogen; radioactive isotopes of the element vary only in their number of neutrons. 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.