Atoms and Molecules. 897 



for any other solid. In the case of such elements as aluminium 

 and lead differing greatly in atomic weight, the edge of the 

 elementary cube lattice is about the same — 4*07 for Al as 

 compared with 4*91 for Pb. 



These distances might conceivably have been many times 

 less than they are, and possibly greater, since the dimensions 

 or the electron above given are of the order of 10 ~ 13 cm., 

 100,000 times smaller. The distances between atoms might 

 easily have been 10~ 9 , 10 ~ 10 , or 10 ~ n cm. unless there is 

 some fundamental cause regulating it that applies to all 

 atoms m common. These considerations lead directly to the 

 thought constituting the theme of this paper, namely, that 

 the general cause contributing to an equilibrium distance in 

 all solids is connected with the properties of the positive and 

 negative electrons themselves common to all atoms. Minor 

 variations in this distance only are brought about by the 

 special configurations of these electrons in the atoms, as in 

 the models. 



It is shown in this paper that the non-spherical shape of 

 the negative electron is the principal cause of this particular 

 value, 10 " 8 cm., which is known to be confined within such 

 narrow limits. 



Not much is known with the same degree of certainty 

 about the distances between the centres of the atoms in the 

 chemical molecules consisting of but a few atoms, but 

 the presumption is that the order of magnitude is the same 

 as in the crystal molecule, the whole crystal being regarded 

 as one molecule, and that the fundamental cause operating 

 to hold these atoms apart is no different in the one case from 

 the other. 



It is still an outstanding question what is the nature of 

 the forces holding atoms at a distance from each other in 

 equilibrium at all, and especially at such uniform distances. 

 Modern atomic theories have postulated many things which 

 depart from electromagnetic theory in their fundamentals 

 in order to obtain some cause for holding two atoms together, 

 as in the diatomic molecule, for example. The Bohr form 

 of theory sets electromagnetic theory aside at the outset in 

 postulating electrons moving in orbits at such speeds that 

 they must lose energy by radiation. The Lewis-Langmuir 

 theory, as extended by Langmuir, does the same thing when 

 it requires an oscillation of an electron back and forth in 

 any form of arc or curve. Without some motion of this 

 kind in the latter theory the system loses stability ; their 

 diatomic molecule becomes a system of four point charges in 



Phil. Mag. S. 6. Vol. 43. No. 257. May 1922. 3 M 



