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An isotope is defined as an atom that has the same number of protons, which determines the element, but a different number of neutrons, leading to variations in the atomic mass of that element. This means that while the atomic number (the number of protons) remains constant, the atomic mass (the total number of protons and neutrons) can vary due to changes in the neutron count.

In the case of 7 protons and 6 neutrons, this corresponds to an isotope of the element with 7 protons, which is nitrogen. Since nitrogen can have different isotopes based on the number of neutrons present, this specific configuration represents a valid isotope, specifically nitrogen-13 (with a mass number of 13).

The other examples provided either have the same neutron count as a well-known isotope or correspond to a different element altogether, making them not representative of isotopes in the same way. Therefore, the configuration of 7 protons and 6 neutrons distinctly illustrates the concept of isotopes, showcasing how the same element can exist in different forms based on neutron numbers.