Consider three 1-gram samples of matter: A, carbon-12; B, carbon-13; C, uranium-238. How do you rank them in terms of having the greatest number of atoms, from least to most?
From least to most.........
How do you know? Well, consider the molar masses of each element. To find the number of moles we multiply thru by the ATOMIC mass of each isotope:
So how does this calculation help us answer the question? Well,
And here, the greatest number of particles necessarily occurred with the element with the LEAST atomic mass, i.e.
Can you work out the actual numbers of atoms in each of the individual quantities?