#1##"mol"# of atoms contains Avogadro's number of atoms. Avogadro's number #=##N_A##=##6.022140857(74)xx10^23#.
Explanation:
So there are #1/4##xx##N_A# nitrogen atoms in such a molar quantity of nitric oxide, approx. #1.5xx10^23# individual nitrogen atoms. How many OXYGEN atoms in such a quantity?
Here I use #N_A# as I would use any other collective number: a dozen, a score, a gross. I am perfectly free to do so, because any physical scientist knows precisely what I mean by a #"mole"#.