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.
Isotopes are atoms that have the same number of protons and electrons, but a different number of neutrons. Changing the number of neutrons in an atom does not change the element. Atoms of elements with different numbers of neutrons are called isotopes of that element.