NO. II STRUCTURE OF THE ATOM — PARSON 7 



chance of their resultant moment being zero altogether too much, for 

 most substances are diamagnetic ; while if the radii are not different 

 enough to prevent interference, an altogether chaotic motion will 

 result in the atom. Hence rotating rings of electrons, where they 

 can exist at all, must be coaxial, and all atoms containing .them must 

 have a magnetic axis. Now the diamagnetism of a substance does 

 not of course extend to its constituent atoms in all cases, for stable 

 molecules of no magnetic moment can be formed from magnetic 

 atoms ; but the diamagnetism of Helium and Argon gases (P. Tanz- 

 ler, Ann. der Phys., 24, 931-938, 1907) must mean that the separate 

 atoms of these elements are diamagnetic. Here it might perhaps be 

 argued that rotating rings of electrons would have a gyroscopic 

 action which, for perfectly independent atoms, would prevent a para- 

 magnetic reaction. But this independence, which cannot be com- 

 plete even in the gaseous state, must be lost in the liquid state, and 

 yet there is no reason to believe that liquid Argon is paramagnetic 

 (as far as can be ascertained, there have been no studied observations 

 on the point) ; nor can the diamagnetism here be explained by the 

 formation of polyatomic molecules. Also it should be observed that 

 in oxygen and nitric oxide we have cases of paramagnetic gases. 



Thus the idea of rings of electrons, which is used in the model 

 atoms of Thomson, Rutherford, and Bohr, is experimentally shown 

 to be untenable. 



If the laws of electrodynamics are to be applied quite rigor- 

 ously—and the present attempt to show that the magneton is 

 fundamentally a better assumption than the classical electron in 

 orbital motion of course requires this test — it may be said of a system 

 of classical electrons that the separate electrons must either be at rest 

 relatively to one another or else be in chaotic motion : in either case 

 there may or may not be an additional rotation of the whole system 

 about some axis passing through the center of the system. Now 

 these conditions do not allow of a state such as was assumed in 

 Thomson's theory of magnetism, as we have just seen, nor of a state 

 such as was assumed in Langevin's theory, which we now come to 

 consider. 



Langevin (Ann. de Chim. et de Phys., 5, 70-127, 1905) assumes 

 that the electrons rotate in individual orbits with radii not much 

 smaller than that of the atom, thus producing average effects similar 

 to those of ordinary current circuits; and that the axes of these 

 orbits may be distributed in all directions. 



