Atoms with the same atomic number and chemical properties in their purest form are called isotopes.

Here's why:

* Atomic Number: The atomic number defines an element. It represents the number of protons in an atom's nucleus. All atoms of a specific element have the same number of protons.

* Chemical Properties: The chemical properties of an element are primarily determined by the arrangement of electrons in its outer shell, which is influenced by the number of protons.

* Isotopes: Isotopes of an element have the same number of protons (same atomic number) but different numbers of neutrons. This difference in neutron count leads to variations in atomic mass, but the chemical behavior remains largely the same.

Example: Carbon-12 and Carbon-14 are both isotopes of carbon. They have the same number of protons (6) but different numbers of neutrons (6 for Carbon-12 and 8 for Carbon-14). Both behave chemically as carbon, but Carbon-14 is radioactive due to its extra neutrons.

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