Is this graphic of molecules correct?
No.  Most molecules of air have two atoms. 

So if you want to be quantitatively accurate, if you have 100 molecules in a graphic, it would show

78 dinitrogen (N-N) molecules 

21 dioxygen (O-O) molecules

1 argon atom (Ar) 

http://eesc.columbia.edu/courses/ees/slides/climate/table_1.html

And you could add some water (H-O-H) molecules if you want to depict humidity.