328 Dr. A. W. Stewart on Atomic Structure 



general appearance of the atomic mechanism is shown in 

 fig.l. 



Fiff. 1. 



1. Orbits of negative electrons. 



2. Orbits of positive electrons. 



3. Cometary electronic orbits. 



It is now necessary to consider each part of the system in 

 detail. The central negative core is the point of origin of 

 the /3-rays ; and since the electrons ejected by the atom 

 during the /3-ray changes travel at extremely high velocities, 

 although they have passed through the positive zone during 

 their flight, it is simplest to assume that under normal con- 

 ditions they are moving at high speeds in their intra-atomic 

 orbits. Charges moving with such high velocities would be 

 difficult to deviate from their normal paths by external forces; 

 and this accounts for the fact that chemical reactions fail to 

 affect the intimate chemical structure of atoms. During 

 phases of atomic instability, however, these electrons would 

 leave the atom at high speeds. 



The intermediate positive zone of the atom is occupied 

 mainly — and in the non-radioactive elements exclusively — 

 by positive electrons, the number of which is equal to the 

 atomic number of the element. In the case of radioactive 

 elements, a further complication most be postulated in order 

 to account for the ejection of a-particles. In the case of 

 these active elements it is assumed that in the positive zone 

 some of the orbits are occupied by complex groups composed 

 of two positive and one negative electron which together 

 form a " planet and satellites " arrangement circulating as a 

 whole about the central negative core. The number of these 

 complexes depends upon the nature of the atom in question : 



