1923] The Search for the Ultimate Atom 45 



tron can vibrate or oscillate in this cell but cannot depart from it. 

 The second shell has a radius of two and hence four times the area 

 of the first. Since all the cells are equal in area this has a capacity 

 for 8 electrons, 4 in each hemisphere, and Ave have the shell for 

 neon. Superposed on this shell is another of approximately equal 

 radius and hence of equal capacity. This is the shell of argon. The 

 next two shells, one superposed upon the other, have the radius 3, 

 hence each can contain 18 electrons and we have the shells for 

 krypton and xenon. The next shell with a radius of 4 accommodates 

 32 electrons and gives us the shell for niton. 



There can be no electrons in the outer shell till the inner ones 

 are completely filled. The atoms with the partially filled shells con- 

 stitute the active elements. The tendency of these outside electrons 

 to combine so as to form stable configurations constitutes chemical 

 action. Quoting from a brief article by Langmuir : ' ' The 8 electrons 

 in the second and third layers are arranged in a symmetrical way 

 like the arrangement of the 8 corners of a cube. This stable group 

 of 8 electrons is called the Octet. The chemical properties of the 

 elements result from the tendency of the individual atoms to take up 

 or give up electrons in order to form Octets." 



This theory has been highly successful in explaining chemical phe- 

 nomena and, says Langmuir, "has made it possible to predict cor- 

 rectly the properties of certain substances before these properties 

 have been determined by experiments." 



The real atom must necessarily incorporate whatever is true in 

 both the Bohr and Langmuir atoms. It seems that in all prob- 

 ability it may be a compromise between the two. 



Wake Forest, N. C. 



