Yes, atoms can have the same atomic number (number of protons) but different mass numbers. This is because atoms of the same element can have different numbers of neutrons in their nuclei, resulting in different mass numbers.
Atoms of the same element with different numbers of neutrons are called isotopes. Isotopes have the same atomic number because they have the same number of protons, which defines the element. However, they differ in their mass numbers, which represent the total number of protons and neutrons in the nucleus.
For example, let's consider the element carbon (C). Carbon has an atomic number of 6, indicating that it has 6 protons in its nucleus. However, carbon has several isotopes, such as carbon-12, carbon-13, and carbon-14. These isotopes have 6 protons each (since they are carbon atoms) but different numbers of neutrons. Carbon-12 has 6 neutrons, carbon-13 has 7 neutrons, and carbon-14 has 8 neutrons. Therefore, they have mass numbers of 12, 13, and 14, respectively.
Isotopes can exhibit different physical and chemical properties due to their different mass numbers, but they share the same atomic number and similar chemical behavior since they have the same number of protons and electrons.