# Why don't equal masses of carbon atoms and oxygen mol. ecules contain the same number of particles?

An isolated carbon atom, $Z = 6$, has 6 protons, and mostly 6 neutrons. An isolated oxygen atom, $Z = 8$, has 8 protons, and mostly 8 neutrons. So if you have equal masses of carbon and oxygen (and this would be fairly hard to manage), you know there are more carbon atoms, because oxygen is more massive than carbon. Capisce?