Welcome to the Community College of the Air Force (CCAF). Our college is a federally-chartered degree-granting institution that serves the United States Air Force's enlisted total force.
Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers, which give the total number of nucleons-the number of protons plus neutrons.
The isotopes of an element are like different versions of an element - they have the same number of protons but different number of neutrons. In turn, we can also say that isotopes of an element have the same atomic numbers but different atomic mass.