Caffeine contains 28.9% of nitrogen. The molecular weight of caffeine is 194. The number of nitrogen atoms present in one molecule of caffeine _______

.  % Composition of an element in the given compound =  $\frac{\text{At.\hspace{0.17em}\hspace{0.17em}wt.\hspace{0.17em}\hspace{0.17em}of\hspace{0.17em}\hspace{0.17em}element\hspace{0.17em}\hspace{0.17em}×\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}No.\hspace{0.17em}\hspace{0.17em}of\hspace{0.17em}\hspace{0.17em}atom\hspace{0.17em}\hspace{0.17em}of\hspace{0.17em}\hspace{0.17em}the\hspace{0.17em}\hspace{0.17em}element}}{\text{Mol.\hspace{0.17em}\hspace{0.17em}wt.\hspace{0.17em}\hspace{0.17em}of\hspace{0.17em}\hspace{0.17em}compound}}\times 100$

            $28.9=\frac{14\times x}{194}\times 100$

            $\therefore x=4$