What is the difference between reacting copper with concentrated nitric acid and dilute nitric acid

I know one produces nitrogen monoxide and the other one produces nitrogen dioxide, but what one is which and why does it occur? (Why does it occur and why does it only occur with copper?)

Thanks

3Cu + 8HNO3 (dilute) --> 3Cu(NO3)2 + 2NO + 4H2O

Cu + 4HNO3 (conc.) --> Cu(NO3)2 + 2NO2 +2H2O

copper isn't really reactive like other metals. look at the activity series linked below, Cu occupies a space near the bottom of the list. in fact, Cu is below H meaning that Cu will have a hard time replacing H in the HNO3 when it is dilute. when concentrated, the acid reacts with the copper better. no H2 is produced