ARTICLES 



LANGMUIR'S THEORY OF THE ARRANGE- 

 MENT OF ELECTRONS IN ATOMS AND 

 MOLECULES.! 



By S. C. BRADFORD, B.Sc, 



Science Museum, London. 



The theory propounded by Langmuir, published in the June 

 number of the Jouryial of the American Chemical Society , 

 explains so wonderfully the properties of elements and com- 

 pounds and brings to light such remarkable relationships, 

 formerly unsuspected, that it necessarily contains a large 

 element of truth. Although, doubtless, it will be subject to 

 considerable modification, the power of the theory is so great 

 that it must have the widest application. 



Hitherto the problem of atomic structure has usually been 

 attacked from the physical point of view, with little considera- 

 tion of the vast store of chemical relationships which, in 

 Langmuir's opinion, provide a better foundation for a theory 

 than the relatively meagre physical data available. Disre- 

 garding for the present the physical evidence in favour of their 

 rotation, the electrons in atoms are assumed to be stationary, 

 or to oscillate about a mean position, in accordance with the 

 stereochemical testimony that the primary valence forces 

 between atoms act relatively in nearly fixed directions. For 

 example, if wood is carbonised under certain conditions, or if 

 tungsten trioxide is reduced in very dry h3^drogen, the resulting 

 elementary substances occupy about the same volume as the 

 original compound. The volumes are about twenty times as great 

 as those of the corresponding elements in their crystalline form. 



The whole behaviour of such bodies tends to show that 

 their atoms are arranged in fixed branching chains, indicating, 

 as Langmuir considers, that the valency electrons are immobile. 



In conformity with this supposition, each atom is conceived 

 as comprising a nucleus of positive charges of electricity around 

 which the electrons are disposed in a definite configuration. 

 The number of unit positive charges in the nucleus is the same 

 as the atomic number of the element, which corresponds to its 

 position when the elements are arranged in order of increasing 

 atomic weight. The equivalent number of electrons or unit 



1 Jour. A mer. Chem. Soc, 1919, 41, 868 ; Hendrick, The Langmuir Postulates, 

 Chem. and Metall. Eng., 1919, 21, 73. 



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