I can't understand how both the atomic weight of one atom of an element and the weight in grams of a mole of that element are the exact same thing. For example helium has an atomic mass of 4.0026. That was obtained by adding the amount of protons and neutrons in a helium atom together. On the other hand 4.0026 is also the weight in grams of 1 mole of helium. Since 1 mole contains the exact same number of atoms regardless of what element it is how is this possible? Did Avogadro carefully plan it out and made sure 1 mole of any element had the exact same weight in grams as the atomic mass unit of any given element?