* Atomic Mass: The mass of an atom is primarily determined by the number of protons and neutrons in its nucleus. Lighter atoms have fewer protons and neutrons.

* Mole: A mole is a specific number of particles (6.022 x 10^23). One mole of any element contains the same number of atoms.

* Mass of One Mole: Since a mole of any element contains the same number of atoms, the mass of one mole is directly proportional to the atomic mass of the element. Therefore, lighter atoms with lower atomic masses will have a lower mass per mole.

Example:

* Hydrogen (H) has an atomic mass of approximately 1 atomic mass unit (amu).

* Oxygen (O) has an atomic mass of approximately 16 amu.

This means that one mole of hydrogen will have a mass of approximately 1 gram, while one mole of oxygen will have a mass of approximately 16 grams.