Foundations of the Universe 1 20:5 



Sir J. J. Thomson imagined the electrons circulating in shells 

 (like the layers of an onion) round the nucleus of the atom. This 

 did not suit, and Sir E. Rutherford and others worked out a 

 theory that the electrons circulated round a nucleus rather like 

 the planets of our solar system revolving round the central sun. 

 Is there a nucleus, then, round which the electrons revolve? The 

 electron, as we saw, is a disembodied atom of electricity; we 

 should say, of "negative" electricity. Let us picture these elec- 

 trons all moving round in orbits with great velocity. Now it is 

 suggested that there is a nucleus of "positive" electricity attract- 

 ing or pulling the revolving electrons to it, and so forming an 

 equilibrium, otherwise the electrons would fly off in all directions. 

 This nucleus has been recently named the proton. We have thus 

 two electricities in the atom : the positive = the nucleus ; the nega- 

 tive = the electron. Of recent years Dr. Langmuir has put out 

 a theory that the electrons do not revolve round the nucleus, but 

 remain in a state of violent agitation of some sort at fixed dis- 

 tances from the nucleus. 



But we will confine ourselves here to the facts, and leave the 

 contending theories to scientific men. It is now pretty generally 

 accepted that an atom of matter consists of a number of electrons, 

 or charges of negative electricity, held together by a charge of 

 positive electricity. It is not disputed that these electrons are in 

 a state of violent motion or strain, and that therefore a vast energy 

 is locked up in the atoms of matter. To that we will return later. 

 Here, rather, we will notice another remarkable discovery which 

 helps us to understand the nature of matter. 



A brilliant young man of science who was killed in the war, 

 Mr. Moseley, some years ago showed that, when the atoms of 

 different substances are arranged in order of their weight, the// 

 are also arranged in the order of increasing complexity of struc- 

 ture. That is to say, the heavier the atom, the more electrons it 

 contains. There is a gradual building up of atoms containing 

 more and more electrons from the lightest atom to the heaviest. 



