The atomic number for carbon dioxide is not applicable because carbon dioxide (CO2) is a compound, not an individual element. However, we can look at the atomic numbers of its constituent elements.
Carbon (C), which is one of the elements in carbon dioxide, has an atomic number of 6. Oxygen (O), the other element in carbon dioxide, has an atomic number of 8. Therefore, while carbon dioxide itself does not have an atomic number, the atomic numbers of the elements that compose it are 6 for carbon and 8 for oxygen.