Why is sulfur dioxide more massive than carbon dioxide?
Because the mass of a carbon atom is much less (approx. 1/3) than that of the sulfur atom.
When we say 1 mole of stuff, we could equally well say another number, 10 or 12, or 20, or 30.
We use the mole because it is a fact that
So I look at the Periodic Table, and it tells me that the atomic mass of elemental
I would carefully examine this and test your understanding. If you can grasp the connection between the micro world of atoms and molecules with the macro world of grams, and kilograms, and litres, you will have grasped much of the conceptual basis of undergraduate inorganic chemistry.