Which of the following describes isotopes?

Isotopes are defined as atoms of the same element that have the same number of protons but different numbers of neutrons. This variation in the number of neutrons results in different mass numbers for the isotopes, since the mass number is calculated by adding the number of protons and neutrons together. For example, carbon-12 and carbon-14 are both isotopes of carbon, where carbon-12 has six neutrons and carbon-14 has eight. This concept captures the essence of isotopes, highlighting the importance of neutrons in distinguishing between them while maintaining the identity of the element based on the number of protons.