The chemistry of the radio-elements / by Frederick Soddy.

  • Frederick Soddy
Date:
1914
Catalogue details

Licence: In copyright

Credit: The chemistry of the radio-elements / by Frederick Soddy. Source: Wellcome Collection.

    53/64 page 41
    found is one less than the atomic number in each case, 19 for calcium and 29 for zinc, instead of 20 or 30, the number of the place these elements respectively occupy in the Periodic Table. For iron, cobalt, and nickel the num- bers are 27, 28, and 29, in agreement with their chemical properties and order in the Periodic Table, though, of course, the atomic weight of cobalt is greater than that of nickel, just as that of argon is greater than that of potassium, or that of tellurium greater than that of iodine. We thus have another definite proof that it is the nuclear charge, rather than the atomic mass, which fixes the position of the element in the Periodic Table. The present ideas of the structure of atoms thus centre round two distinct regions, and it is probable that a third distinct intermediate region will have to be postulated. There is the exceedingly small nucleus, consisting of the << sub-atoms of matter in association with positive electricity, —on the average approximately unit charge per two units of mass—and a few negative electrons only. The charge is thus overwhelmingly positive, and its variation, unit by unit, gives the successive places in the Periodic Table. Then there is the outer region of the atom, which alone is concerned in chemical and in almost all the common physical phenomena, and this consists of sufficient negative electrons to com- pensate the central positive charge, or one, two, three, and so on less than this in the case of the uni- or multi-valent ions of the elements. How many, or rather how few, of these electrons are directly concerned in these phenomena cannot be said, but probably, from the periodicity of atomic properties, only the outermost ring or shell of the structure. Lastly, it is necessary to differentiate an inner ring or shell of electrons, to account for the production of characteristic X-rays and some of the newer phenomena exhibited by matter.
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