1815 – UK
‘Atoms are not the smallest thing’
After ANTOINE LAVOISIER had compiled his list of the then known elements, another 32 were added in the years following his death. Fifty kinds of fundamental building blocks for matter seemed excessive. In 1815 Prout, using AVOGADRO’s method of comparing the relative densities and weights of gases, proposed that all atoms appeared to have weights that were exact multiples of the weight of the lightest atom, hydrogen, and that the different atomic weights of elements are whole-number multiples of the atomic weight of hydrogen (Prout’s hypothesis).
He took this as proof that all atoms were actually made from hydrogen atoms and the idea was adopted as atomic theory and used for later investigations of atomic weights and the classification of the elements.
If all atoms are made from atoms of hydrogen, then it could be possible to transform an atom of one element into an atom of another.
If atoms had been assembled from other things, then they themselves could not be the smallest things in creation.
Apart from the method of weighing atoms being controversial, there are exceptions to the rule. Chlorine is 35.5 times as heavy as hydrogen.