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 number of neutrons in the nucleus of an element determines the isotope of the element. All elements have a particular isotope that is most common in nature. For example, the most common isotope of hydrogen has no neutrons, but isotopes exist with 1 neutron (called deuterium) and 2 neutrons (called tritium).