This Demonstration lets you browse the properties of isotopes of chemical elements by selecting the atomic number and atomic mass number. The atomic mass number is equal to the sum of the numbers of neutrons and protons in the nucleus; the atomic number is the periodic table number, equal to the number of the protons. The tabulated properties include isotope abundance, spin, magnetic and quadrupole moments, half-life for unstable isotopes, and mass excess (the difference between the actual mass and the mass number).