In the context of chemistry, what does the term 'isotope' mean?

The term 'isotope' specifically refers to atoms of the same element that have the same number of protons but different numbers of neutrons. This difference in neutron count leads to variations in atomic mass, while the chemical properties remain largely the same because they are determined by the number of protons and electrons, which define the element.

For instance, carbon has several isotopes, including carbon-12 (with 6 neutrons) and carbon-14 (with 8 neutrons). Both are carbon because they have the same number of protons (6), but the difference in neutrons means they have different masses and some variations in stability, especially in the case of carbon-14, which is radioactive.

In contrast, other options do not accurately capture the definition of isotopes. Atoms of different elements having the same mass would not qualify as isotopes, since they involve different elemental identities. Atoms with a different number of protons describe different elements entirely, and atoms with variable mass and charge do not pertain specifically to isotopes but rather suggest a range of ions or other atomic variations that extend beyond the definition's focus on neutron differences.