In 1 mole of O2, there are 2 moles of oxygen atoms. This is because the chemical formula for oxygen gas (O2) indicates that each molecule of O2 contains two oxygen atoms bonded together. Since 1 mole of a substance contains Avogadro's number of particles, which is approximately 6.022 × 10^23, there are 2 × 6.022 × 10^23 oxygen atoms in 1 mole of O2.