Chemical element whose atoms have seven protons each in their nuclei.

In the context of relativity, more concretely: cosmology, nitrogen is interesting as an indicator of chemical evolution: Its nuclei are not produced during Big Bang Nucleosynthesis, but they are produced by nuclear fusion reactions in the interior of stars. The presence of nitrogen (or, for that matter, of other elements such as oxygen or iron) in an astronomical object is an indicator that stellar fusion has taken place, and hence that the abundances of the different elements do not reflect the element abundances in the early universe.