<prompt> Substances with same atomic number but different mass number areIsotopesIsobarsIsomersAny of the above  <response>: Ans. a Isotope Ref. Radioactive isotope in Medicine Biology by Quimby, 2nd ed., 26TermDefinitionisotopesAtoms having same:- atomic number same number of protons,- position in periodic table, and- chemical and metabolic properties, but diffeient;- number of neutrons,- mass number protons plus neutrons,- density and other physical properties. E.g., 17CI-35, 17CI-37.IsobarsAtoms having same mass numbers, different atomic number hence different neutron number e.g., 28Ni-64, 30Zn-64IsotonesAtoms having same neutron number, different atomic mass number, e.g., 18A-40IsomersAtoms having same atomic and mass numbers but different energy states in nucleus 