26 ILLINOIS ACADEMY OF SCIENCE. 



I will not attempt to discuss how the theory of electrons 

 explains the varied phenomena of electricity and magnetism. 

 Before passing on to its application in chemistry, I will speak 

 of only two or three of the conclusions which have been reached. 

 The electron may be defined as an atom of negative electricity 

 and the current through a metallic conductor seems to be an 

 actual flow of electrons in one direction. In the vacuum tube 

 the electrons or cathode rays fly also only in one direction, but 

 if the cathode is perforated and a residual gas is present, posi- 

 tively charged atoms or molecules may be shot in the opposite 

 direction, of course at a much lower velocity because of their 

 enormously greater mass. These atoms form the canal rays of 

 Goldstein. In electrolytes the electrons no longer move independ- 

 ently as in metallic conductors, but attach themselves to the 

 so-called negative atoms or groups and move slowly in one direc- 

 tion, while the positive atoms or groups — those which have lost 

 an electron — move in the opposite direction. We have long known 

 the metals as the positive portion of electrolytes. It is only 

 recently that this property has been connected with the electrical 

 conductivity of metals. According to the electron theory, a 

 metallic atom forms the positive portion of an electrolyte because 

 it has lost one or more electrons. A metallic wire conducts elec- 

 tricity because it allows the electrons in or associated with the 

 atoms to slip along easily from one atom to another, since the 

 electrons easily escape from the individual atom. 



Several authors have discussed the nature of chemical combina- 

 tion in the light of the electron theory. The most elaborate dis- 

 cussion is that of J. J. Thomson.^ His fundamental assumption 

 is that atoms are composed of a group of electrons within a uni- 

 form sphere of positively electrified matter. A single electron 

 would go to the center of such a sphere. Two electrons, owing 

 to their mutual repulsion, would be in equilibrium at a distance 

 from each other equal to the radius of the sphere. Three elec- 

 trons would form an equilateral triangle, four a tetrahedron, six 

 an octohedron ; but Professor Thomson says that he has been 

 unable to solve the general problem for ii electrons distributed in 

 a sphere. He gives, however, a rather remarkable solution on the 

 supposition that the electrons are situated in a plane. In that 

 case they will arrange themselves in concentric rings and for a 

 given number of electrons there is only a single stable arrange- 

 ment. Further than this, with a given number in the exterior 



'Philosophical Magazine, March, 1904. 



