Mendeleev seized upon the periodicity of elements arranged according to atomic weights and valencies, to provide the rules for what he called his game of
‘chemical solitaire’, each card in his deck marked with the names or symbols of the elements, their weights and chemical properties - realising the potential in Francis Bacon’s ‘shuffle of
things’ in the most literal way.
The potency of Mendeleev’s table was not just that it functioned as a tool for arranging properties but that the gaps in the sequences predicted ‘the
discovery of yet unknown elements’ (as first happened with gallium); that it became evident when an atomic weight may require emending; and that the properties of known and unknown elements could be predicted
from their position.
For Mendeleev, as a philosopher-chemist, who wrote on such things as the “Unity of Matter”, the success of his table triumphantly proclaimed the
value of what we would call theoretical modelling in the face of narrow empiricism. His “Faraday Lecture” in 1869 not only provided telling reviews of the rationale and development of his system but also
delivered a powerful defence of conceptual structuring as a fundamental complement to the experimental method. He constantly resorted to “agreement between theory and experiment; in other words, to
demonstrated generalisation and to the approved experiment”.
He proclaimed that ‘sound generalisation - together with the relics of those which have proved to be untenable - promote scientific productivity, and ensure the
luxurious growth of science under the influence of rays emanating from the centres of scientific energy’. At one point in his lecture, he told how ‘the inductive or experimental method of studying Nature
gained a direct advantage from the old Pythagorean idea’.