Why do isotopes of the same element have nearly identical chemical behavior?

Isotopes of the same element exhibit nearly identical chemical behavior because their chemical properties are determined by their electronic structure, specifically the number and arrangement of electrons in their valence shells.51

In a neutral atom, the number of electrons is equal to the atomic number (Z), which represents the number of protons in the nucleus. Because all isotopes of a given element possess the same atomic number, they also contain the same number of electrons. Since these electrons dictate how an atom interacts with others to form chemical bonds, isotopes behave chemically in the same way.2345

While isotopes differ in the number of neutrons in their nuclei—which affects their atomic mass and physical properties—these variations have a negligible impact on the electronic configuration that governs chemical reactions. Consequently, chemists generally do not distinguish between isotopes during most chemical processes.6347