Isotope
Atoms of one and the same chemical element with the same number of protons (same atomic number) but different number of neutrons and hence a different nuclear number. Isotopes have the same chemical but different nucleonic characteristics.
Atoms of one and the same chemical element with the same number of protons (same atomic number) but different number of neutrons and hence a different nuclear number. Isotopes have the same chemical but different nucleonic characteristics.