Here's why:

* Avogadro's Number: This fundamental constant in chemistry states that one mole of any substance contains 6.022 x 10^23 particles (atoms, molecules, etc.).

* Moles and Atoms: A mole is essentially a unit of measurement for the amount of a substance, defined by the number of particles it contains.

Therefore, regardless of the element's atomic weight or density, one mole of gold, helium, or lead will always contain 6.022 x 10^23 atoms.