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Why do isotopes have similar chemical properties but different masses?

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Bohr model diagram of a hydrogen atom showing a green nucleus labeled H, a single electron orbit, and text with atomic mass 1.008 and electron configuration 1. — atom The Bohr model describes the structure of atoms, in this case hydrogen.

Isotopes of a chemical element have nearly identical chemical properties because they possess the same number of protons and electrons, which determines their position in the periodic table and their chemical behavior. Specifically, the chemical properties of an atom are determined by the arrangement of electrons in its outermost valence shell. Since isotopes share the same atomic number, they have the same number of electrons and thus exhibit the same chemical reactivity.1234

Conversely, isotopes have different masses because they contain a different number of neutrons in their nuclei. While the number of neutrons affects the total atomic mass and physical properties of the atom, it does not influence the electron configuration that governs chemical bonding and reactions. Therefore, while isotopes are chemically indistinguishable in most contexts, they are physically distinct due to their varying mass numbers.421