* Atomic Mass: The atomic mass of oxygen is approximately 16 atomic mass units (amu), while the atomic mass of hydrogen is approximately 1 amu.

* Ratio: Oxygen is therefore about 16 times heavier than hydrogen.

* Moles: A mole is a specific number of atoms (Avogadro's number). The mass of a mole of oxygen is 16 grams, while the mass of a mole of hydrogen is 1 gram.

Therefore, 1 mole of oxygen atoms is 16 times heavier than 1 mole of hydrogen atoms.