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

  • Soddy, Frederick, 1877-1956.
Date:
1914
Catalogue details

Licence: In copyright

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

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    potential ct-pcirticlcs or hsliuin atoms> for which four units of mass correspond with two units of charge, the positive eharge would be about 120. Whereas, if hydrogen is a second ultimate constituent of atomic structure, since for hydrogen unit mass corresponds with unit charge, the number would be still greater. It is clear, therefore, that in dealing with the nuclear charge we must distinguish between the algebraical and arithmetical sum of the opposite charges. It is the algebraic sum—that is, the difference between positive and negative—which fixes the position of the element in the Periodic Table. Isotopes of the first class might be defined as elements for which the algebraic nuclear charge is the same, but the arithmetical nuclear charge is different. Chemical and electro-chemical changes of valency are con- cerned with electrons in the outermost ring, and are reversible by loss or gain of electrons from without. Radioactive changes are concerned with changes in the inner nucleus, and such changes are not reversible by loss or gain of electrons from the ring. But it is the electrical charge of the nucleus which, primarily, controls the power of the ring to lose or gain electrons from without, and controls, therefore, its chemical and most of its physical properties. A. van der Broek’s view as to the magnitude of the intra-atomic charge has recently received a most remarkable confirmation by an entirely new method.®^ The recently discovered power of crystals to reflect X-rays has had already remarkable results in crystallography. It has also enabled the wave-length of the X-rays themselves to be accurately measured. Moseley used as anti-cathodes for the production of the X-rays a series of metals occupying the successive places of the Periodic Table between calcium and zinc, excepting scandium. In each case X-rays of two definite wave-lengths and different intensity, the charac- teristic type of X-rays for these elements were found to be emitted. The wave-lengths of the stronger rays alone have been dealt with as yet. It was found that the frequency of this ray is connected by a simple relation, deduced from Bohr's theory, with a fundamental quantity which increases in units as we pass from one element to the next, and which can only be the charge of the central positive nucleus. The number so far