An atom that has an atomic number of 38 and a mass number of 88 is an isotope of an atom that has An atom that has an atomic number of 38 and a mass number of 88 is an isotope of an atom that has an atomic number of a. 38 and a mass number of 86. b. 50 neutrons and 38 protons. c. an atomic number of 39 and a mass number of 88. d. 50 protons and 38 neutrons.