Der Bau der Atome und die physikalischen und chemischen Eigenschaften der Elemente. Offprint from: Zeitschrift fur Physik, Bd. 9, Heft 1/2, 1922. BOHR'S SECOND ATOMIC THEORY

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First edition, very rare offprint, of Bohr's 'second atomic theory'. "According to this theory, electrons [in an atom] make up various groups and subgroups corresponding to certain quantum numbers and approximate elliptical orbits. These groups were sometimes called 'shells', but they were not shells in the ordinary meaning of the term. During their orbital motions some of the electrons penetrate the region of internal electrons, causing a coupling of the revolving electrons, whose numbers and motions are governed by the correspondence principle" (Kragh, Niels Bohr and the Quantum Atom, 2012, p. 274). Bohr lectured on his second theory before the Physical Society, Copenhagen, on 18 Oct. 1921. "The published versions of the lecture - in Danish, German, English, French and Russian - attracted much attention and helped his theory become widely known. Ehrenfest, who at the end of 1921 stayed at Bohr's institute, wrote enthusiastically to Einstein about all the wonderful things that happened in Copenhagen. Bohr - whom he described as 'a tremendous physicist' - whould soon publish his lecture. 'He presents how he has now interpreted the structure of all atoms. Both methodologically and as regards its results this is something quite enormous'" (Kragh, p. 275). The work is in three parts: the first is on the spectrum of hydrogen; the second is on the series spectra of the elements; the third is on the structure of the atom and the physical and chemical properties of the elements. "Bohr's theory of the periodic system of the elements, based essentially on the analysis of the evidence of the spectra, renewed the science of chemistry by putting at the chemists disposal rational spectroscopic methods much more refined than the traditional ones. This was dramatically illustrated in 1922, by the identification, at Bohr's institute, of the element with atomic number 72. This discovery was made by Coster and Hevesy, under the direct guidance of Bohr's theoretical predictions of the properties of this element; they gave it the name 'hafnium,' from the latinized name of Copenhagen. The conclusive results were obtained just in time to be announced by Bohr in the address he delivered when he received the Nobel Prize in physics for that year" (DSB). 8vo, pp. 67. Original printed wrappers (spine worn, wrappers browned, front wrapper with two closed tears and chipped at fore-edge). N° de ref. del artículo ABE-1572791999320

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