No, there are no two different elements that have exactly the same atomic numbers but different masses or atomic weights. The atomic number uniquely identifies an element and corresponds to the number of protons in the nucleus. Different elements have different atomic numbers, and this is the key factor that distinguishes one element from another.
However, there can be isotopes of the same element that have different masses or atomic weights. Isotopes of an element have the same atomic number (same number of protons) but differ in their number of neutrons, which affects their mass. Isotopes of an element exhibit similar chemical properties but may have different physical properties due to differences in their atomic masses.
So, while isotopes of the same element can have different atomic masses, they still have the same atomic number. But when it comes to different elements, they will always have different atomic numbers, which is the fundamental characteristic that distinguishes one element from another.