Isotopes of the same element have what in common?

Isotopes of the same element share the same atomic number, which means they have the same number of protons in their nuclei. This aspect is crucial because the atomic number defines the element itself. However, isotopes differ in their mass numbers, which arises from the variation in the number of neutrons present within the nucleus. While the number of protons (atomic number) remains constant, the additional neutrons increase the total mass of the atom, resulting in different isotopes of the same element that have unique mass numbers.

For example, carbon isotopes include carbon-12 (with 6 protons and 6 neutrons) and carbon-14 (with 6 protons and 8 neutrons). Both forms are carbon, so they share the same atomic number of 6, but their mass numbers are 12 and 14, respectively, due to the differing neutron counts.

This understanding is key in fields such as chemistry and environmental science, where isotopes can influence the behavior and interactions of elements in various processes.