INTRODUCING "ATOMIC NUMBERS"

MOSELEY, H.G.J. - ESTABLISHING ORDER IN THE PERIODICAL TABLE OF ELEMENTS (PMM 407).

The High-Frequency Spectra of the Elements.

London, 1913.

Without wrappers, but stitched. In "Philosophical Magazine and Journal of Science", Vol. 26, No. 156. December 1913. Pp. 937-1058 a. 6 plates.(= the whole issue No 156). Moseley's paper: pp. 854-860 a. 1 plate. Fine and clean.

First edition of this groundbreaking paper which Rutherford considered A WORK ON PAR WITH THE VERY DISCOVERY OF THE PERIODICAL TABLE, introducing the concept 'Atomic Number'.

Moseley notes a regularity in the shifting of spectral lines when the elements (he examines 50 elements) are arranged according to atomic weight. He finds that bombardments of the various elements with cathode rays yeilds a systematic sequence of vibration frequencies, and from this he derives the concept of atomic number, which he recognizes as equal to the nuclear charge.

"Moseley, working under Rutherford at Manchester, used the method of X-ray spectroscopy devised by the Braggs to calculate variations in the wave-lenght of the rays emitted by each element. These he was able to arrange in a series according to the nuclear charge of the element. Thus if the nuclear charge of hydrogen is 1, in helium it is 2, in lithium 3, and so on by regular progression to uranium as 92. These figures Moseley called atomic numbers.he pointed out that they also represented a corresponding increase in extra-nuclear electrons and that it is the number and arrangement of these electrons rather than the atomic weight that determines the properties of an element. It was now possible to base the periodical table on a firm foundation, and to state with confidence that the number of elements up to uranium is limited to 92. When Moseley'stable was completed, six atomic numbers had no corresponding elements; but Moseley himself was able to predict the nature of four of the missing elements."(Printing and the Mind of Man No. 407). Another paper on the same subject was published by Moseley the next year (1914).

An important paper by Rutherford and Richardson is withbound: Analysis of the gamma rays of Thorium and Actinium Products. Pp.937-948 and 1 plate.

Order-nr.: 41566