What is the difference between isotopes?

Isotopes are defined as atoms of the same element that possess the same number of protons, which is characteristic of the element itself, but they differ in the number of neutrons present in their nuclei. This variation in neutron count leads to different atomic masses for the isotopes of that element. For example, carbon has two stable isotopes: carbon-12 (with 6 neutrons) and carbon-14 (with 8 neutrons). Despite having different masses due to the differing neutron counts, both isotopes maintain the same chemical properties because they have the same number of protons, which determines their identity as carbon and influences their electronic configuration.

The other options present misunderstandings about the nature of isotopes or confuse isotopes with other atomic characteristics.