The ratio of nitrogen atoms (N) to oxygen atoms (O) in the compound N₂O₅ is 2:5. This is because the formula indicates that there are 2 nitrogen atoms and 5 oxygen atoms in each molecule of N₂O₅.

However, you also mentioned NO₂. While the ratio of N:O in NO₂ is indeed 1:2, this is not the same as the ratio in N₂O₅.

It's important to understand that the formulas of chemical compounds determine the specific ratio of atoms within each molecule.