# How many oxygen atoms does 1 mol of O_2 gas have?

You specify a mole of oxygen molecules. This is a mole, Avogadro's number, of ${O}_{2}$ species.
Clearly there are $2 \times {N}_{A}$ oxygen atoms, where ${N}_{A} = \text{Avogadro's number} ,$ $6.022 \times {10}^{23}$.