1905.] 



on the Structure of the Atom. 



59 



certain distance, and that the system can hold three floating magnets 

 in stable equilibrium at a finite distance from its centre. 



An atom analogous to the one we have just been considering 

 would have the power of keeping three positively electrified particles 



Fig. 6. 



in stable equilibrium, provided these are placed at suitable distances 

 along the lines A\ B^ 0^ With other arrangements of cor- 

 puscles, we should get atoms able to keep negatively electrified par- 

 ticles in equilibrium. Thus, for example, if we have 5 corpuscles 

 placed at the corners of a double pyramid as in Fig. 7, then along 

 the lines OA, OB, OC, at suitable distances 

 from negatively electrified particles could 

 be in equilibrium, even if the atom were un- 

 charged. If, however, the central atom were 

 uncharged while the satellites were charged, the 

 molecule, as a whole, would be charged, whereas 

 we know^ the molecule is electrically neutral ; we 

 must consider, therefore, what would be the 

 effect of giving a charge of electricity to the 

 central atom. 



In the case of the three corpuscles, if we gave 

 a negative charge to the central atom, the axes 

 A^, B\ C^, might or might not cease to 

 be axes of stable equilibrium for positively elec- 

 trified particles. The effect of the charge would be to bring the point 

 D of equilibrium closer to the atom — how much closer would depend 

 upon the charge given to the atom ; but as long as D kept outside 

 the atom, stable equilibrium for positively electrified particles would 



