Question #0fe2a

1 Answer
May 17, 2017


Yes, every element has a fractional mass.


Of the first 92 elements, 66 consist of more than one stable isotope, so they have fractional atomic masses.

Even the 26 elements that consist of a single isotope have a fractional mass because of the mass defect — the difference between the actual mass and the sum of the masses of the individual protons and neutrons.

For example, the atomic mass of beryllium-9 is 9.012 g/mol, not 9.000 g/mol.