Rutherford, the alchemist
By 1919, Rutherford’s experimental intuition and curiosity was known around the world. His simple experiments had dominated the field of radioactive studies, and that year he would become the first human to achieve an age-old dream; he became the first alchemist… Legend tells us that one of Rutherford’s students detected hydrogen when putting a chunk of Radon in a vacuum vessel; Rutherford instantly knew there was something special happening, and quickly developed an experiment that proved radioactivity was breaking up nitrogen into oxygen and hydrogen. He published the results in a paper called “Collision of alpha Particles with Light Atoms. IV. An Anomalous Effect in Nitrogen.”, and set out to use these results to further expand his model of the atom. He imagined the nitrogen atom, or rather its nucleus, made up of many hydrogen nuclei, while oxygen was made of one fewer hydrogen nucleus. With this idea Rutherford could construct any atom by grouping protons together, and could explain their increasing mass. This was different from what Harry Moseley had done to support Bohr's model of the atom (classifying them by x-ray emissions); this was a classification by atomic mass. And so, with this idea in mind, Rutherford’s intrepid student, Francis Aston, set out to “weigh” the atom using similar techniques as those developed to weigh the electron. Aston developed the first spectrograph and unleashed a whole new science while discovering isotope after isotope and further revealing the mysteries of matter. But there was a problem… the classification didn’t add up. For example, a helium atom is four times heavier than a hydrogen atom, but only has one more proton. This couldn’t be fully explained by Rutherford’s atomic model; there was something missing. This puzzled the scientific community for over a decade.
Source: Rutherford, E. (1919). LIV. Collision of α particles with light atoms. IV. An anomalous effect in nitrogen. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 3(222), 581–587.
License CC BY 4.0
Back to archive
Full disclosure, I may occasionally borrow a sentence from Will Durant's Story of Civilization. I absolutely love that collection!