The ratio of the mass defect of an isotope to its mass number, equal to (M − A) ÷ A, where M is the atomic mass and A is the mass number: usually expressed as parts per 10,000
The difference between the isotopic mass and the mass number of a nuclide, divided by its mass number, often interpreted as a measure of stability.
The ratio of the total volume of a set of objects packed into a space to the volume of that space.
The difference between the isotopic mass of a nuclide and its mass number, divided by its mass number. The packing fraction is often interpreted as a measure of the stability of the nucleus.