Calculate the number of oxygen atoms in 1 mole of O₂.

1 molecule of O₂ has 2 oxygen atoms

So, 1 mole of O₂ will contain 2 mole of oxygen atoms

Now, one mole of each substance has 6.022 x 10²³ molecules/atoms/particles.

Therefore,

1 mole of O₂ = 2 x 6.022 x 10²³

= 12.044 x 10²³ oxygen atoms