No, atoms cannot have the same atomic number but different mass numbers. The atomic number of an atom represents the number of protons in its nucleus, which uniquely identifies an element. The mass number, on the other hand, represents the total number of protons and neutrons in the nucleus of an atom.
Since the atomic number is determined by the number of protons, atoms with the same atomic number must belong to the same element. However, atoms of the same element can have different mass numbers if they have different numbers of neutrons. These different forms of an element, with varying numbers of neutrons, are called isotopes.
Isotopes of an element have the same atomic number but different mass numbers. For example, carbon-12 and carbon-14 are both isotopes of carbon, meaning they have the same number of protons (atomic number 6), but carbon-12 has 6 neutrons, while carbon-14 has 8 neutrons.