Prout's Hypothesis

the hypothesis that hydrogen is the primary material from which the atoms of all the other elements were formed by means of a particular type of condensation. This idea was expressed in 1816 by the English physician and chemist W. Prout (1785–1850). It proceeded from a study he published in 1815, in which he concluded the following: if the atomic weight of hydrogen were set equal to 1, then the atomic weights of all the other elements should be expressed as whole numbers. Prout believed that deviations from the integrality of atomic weights were due to errors in measurement. However, the very precise determinations of atomic weights carried out by J. Stas, J. de Marignac, and T. Richards in the second half of the 19th and the early 20th century did not support this view.

The historical significance of Prout’s hypothesis is that it was the first scientific hypothesis to deal with the complexity of atomic structure and that it stimulated research to determine the precise atomic weights of chemical elements.