Nitrogen (N) is the element with atomic number 7, symbol N. It is the most common isotope has atomic weight 14, with 15 being another stable isotope.
It is very stable in its molecular form, N2, with a triple bond and typically it is easer to convert another compound to N2 than the reverse. It is volatile in its atomic form.
Nitrogen molecules are thought to be broken (e.g., "fixed", converted to ammonium, NH4+) through UV Emission, lightening, and energetic particles.
The Spectral Lines of atomic nitrogen are grouped into NI (neutral nitrogen), NII (singly ionized), NIII (doubly ionized), etc.