Project Gutenberg #72875
The A B C of Atoms
Bertrand Russell
1923Russell's popular explanation of electrons, nuclei, spectra, quanta, and radioactivity as physics stood in the early 1920s.
Project Gutenberg #72875 Public domain in the United States Cover source Local typographic cover created for The Missing Workbook from public-domain source metadata
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hydrogen. Nevertheless, what is known is sufficient to place it beyond reasonable doubt that the explanation of the spectrum of other elements is the same in principle as in the case of hydrogen. There is one case which can be tested to the full, and that is the case of positively electrified helium, which has lost one electron and has only one left. This only differs from hydrogen (as regards the movements of the electron) by the fact that the charge on the nucleus is twice as great as that on the electron, instead of being equal to it, as with hydrogen, and that the mass of the nucleus is four times that of the hydrogen nucleus. The changes which this produces in the spectrum, as compared with hydrogen, are exactly such as theory would predict.
In the present chapter, we have seen what was the conclusion to which Bohr was led as to possible states of the hydrogen atom, but we have not yet seen what was the reasoning by which he was led to this conclusion. In order to understand this reasoning, it is necessary to explain what is called the theory of quanta, of which Bohr’s theory of the atom is a special case. The theory of quanta will be the subject of the next chapter.