It is argued that the scale of atomic masses rests far too heavily on two possibly dubious pieces of evidence. These are the nineteenth-century determination of the atomic weight of hydrogen, and early mass spectrographic work on the determination of atomic masses. The determination of the atomic weight of hydrogen is possibly prone to overestimation because of adventitious enrichment in deuterium during the experimental procedure. The mass spectrographic work is likely to be susceptible to both systemic and theoretical errors deriving from the assumptions employed; it is also possibly enmeshed in the confusion between the (then prevailing) chemical and physical scales of atomic weight. All these ambiguities may well have led to a dubious confirmation of the atomic mass of hydrogen. The idea of the ‘mass defect’, deriving from this work, formed a corner-stone of the subsequently developed theory of the structure of the atomic nucleus. A particular problem with the mass-defect idea is that, by mass-energy equivalence, heavier atoms would be less stable than lighter ones. (Thus, the mass defect may well be an artefact deriving from the inherent inaccuracies of early mass-spectrographic studies.) All this has apparently led to a dubious theory of nuclear structure. Thus, the balance between the electrostatic and strong forces should favour the latter with increasing atomic mass – contrary to current theory, which apparently neglects to take account of the predominance of nearest-neighbour interactions between nucleons. Consequently, the origins of nuclear energy, whether by fission or fusion, seem unclear. Taken as a whole, these arguments indicate a fundamental reappraisal of current theoretical ideas: It would appear that mass-energy equivalence may be involved more fundamentally and insidiously in the generation of nuclear energy; it is also possible that the radionuclides arise by the malformation of nuclei during their creation, a consequence of their mass and size.