Recall that isotopes are atoms of the same element that have the same number of protons but differ in the number of neutrons.
Understand that the atomic number of an element is defined by the number of protons in its nucleus, which remains constant for all isotopes of that element.
Recognize that the chemical symbol represents the element itself and does not change between isotopes.
Therefore, the key difference between isotopes lies in the number of neutrons, which affects the atomic mass but not the atomic number or chemical properties significantly.
Summarize that isotopes differ in their number of neutrons, while their number of protons (atomic number) and chemical symbol remain the same.