The chemical nature of element 72, subsequently named hafnium, is generally regarded as a prediction from Bohr's theory of the periodic system and hence as a prediction from quantum theory. It is argued that both of these views and in particular the latter are mistaken. The claim in favour of Bohr's theory is weakened by his accommodation of independent chemical arguments and the claim in favour of quantum theory is untenable since the prediction is not strictly deductive.

The current status of explanation worked out by Physics for the Periodic Law is considered from philosophical and methodological points of view. The principle gnosiological role of approximations and models in providing interpretation for complicated systems is emphasized. The achievements, deficiencies and perspectives of the existing quantum mechanical interpretation of the Periodic Table are discussed. The mainstream ab initio theory is based on analysis of selfconsistent one-electron effective potential. Alternative approaches employing symmetry considerations and applying group theory usually require some (...) empirical information. The approximate dynamic symmetry of one-electron potential casts light on the secondary periodicity phenomenon. The periodicity patterns found in various multiparticle systems (atoms in special situations, atomic nuclei, clusters, particles in the traps, etc) comprise a field for comparative study of the Periodic Laws found in nature. (shrink)