the Molecule and Chemical Combination. 



525 



Lothar Meyer. Thus, Gervaise le Bas, ' Molecular Volume 

 •of Liquid Chemical Compounds/ p. 237, says : — 



" 1. There is a periodic relation between the atomic volume 

 and the atomic weight of the elements. 



2. There is a tendency for the atomic volume to diminish 



in each series as the atoms increase in weight. Thf3 

 smallest occur in group 7. 



3. There is a general increase in the atomic volume of 



the members of each group from series one on- 

 wards, that is in the direction of increasing atomic 

 weight." 



This is in entire agreement with the results we have just 

 found. The same thing is beautifully shown by the expe- 

 riments of W. L. Bragg (Phil. Mag. xl. p. 169, 1920), 

 which give a curve (rig. 4) for the atomic radii which for 



Fig-. 4. 



?w? 



M F 



"V? 



the period from lithium to neon agrees remarkably well 

 with the figures given above. 



We should expect, since the law of force we have assumed 

 is probably only an approximation holding near a position of 

 equilibrium, that the relative values of the radii of the 

 elements within one period would be more reliable than 

 those for elements in different periods as the value of cc would 

 vary from one period to another. 



Work required to separate one electron from the atom. 



The work required to separate an electron will depend 

 upon whether the electron is ejected so quickly that the 

 electrons left in the atom have not had time to alter their 

 positions appreciably before the ejected electron has passed 

 out of the sphere of their influence, or whether the process 

 takes place so slowly that the other electrons subside 

 gradually into positions of equilibrium without acquiring 

 any kinetic energy. If W l5 W 2 represent the amounts of 



