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 two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element.