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 of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as 1H, 2H and 3H, with the mass number at top left. When the atomic nucleus of an isotope is unstable, compounds containing this isotope are radioactive.Tritium is an example of a radioactive isotope.sotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as 1H, 2H and 3H, with the mass number at top left. When the atomic nucleus of an isotope is unstable, compounds containing this isotope are radioactive. Tritium is an example of a radioactive isotope.