At STP, 1 liter of #O_2#(g) and 1 liter of #Ne#(g) have the same what?
Have the same number of particles.........
Equal volumes of gases at the same temperature and pressure, have the SAME number of particles whizzing around their respective containers. You could work out the number of particles of each gas precisely:
Of course, the different gaseous samples, will have different MASSES, in that the mass of a