Question

explain why nitrogen atom join up to form nitrogen molecules

Answer 1

Atoms join together to make compounds because the compounds made are more stable than the what it was before (atoms). It has much to do with interactions of the electrons. Atoms become stable when the achieve octet valence electrons (8 electrons in in outer most shell). Although most atoms (besides noble gases) do not have the stable octet valence electrons to start off with, when compounds are made, the octet valence electrons is made most of the time.