Why do isotopes of the same element have the same chemical properties?

Isotopes of the same element have the same chemical properties because they have the same number of electrons. The chemical properties of an element are determined primarily by its electron configuration, particularly the arrangement of electrons in the outer shell (valence electrons). Since isotopes are variants of the same element, they have identical atomic numbers, which means they possess the same number of protons and also the same number of electrons, although they differ in the number of neutrons.

This similarity in electron count leads to identical chemical behavior. The different masses of isotopes, due to the varying number of neutrons, do not significantly affect how these atoms interact chemically or their behavior during chemical reactions. Therefore, all isotopes of a specific element will display the same chemical properties despite their differences in mass.