INTRODUCING "ATOMIC NUMBERS" - PMM 407

MOSELEY, HENRY GWYN JEFFREYS.

The High-Frequency Spectra of the Elements. Part (I-) II.

London, Taylor and Francis, 1913-14. 8vo. Bound in two recent uniform full cloth bindings with gilt lettering to spines and front boards. Extracted from "The London, Edinburgh and Dublin Philosophical Magazine" Sixth Series Volume 26 Nos 156 and 160, entire issues offered. A fine and clean set. Pp. 1024-1034 + 1plate; pp. 703-713.

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).

Order-nr.: 57201