POPULAR SCIENCE 631 



hydrogen nuclei, each carrying unit positive charge, and be- 

 tween these nuclei the two electrons rotate in an orbit the 

 plane of which is at right angles to the imaginary line joining 

 the two nuclei. This system has been shown to be a stable 

 one, provided the nuclei as they vibrate to and fro do not 

 exceed certain limits of amplitude. There is a similar limita- 

 tion to the diameter of the orbit of the electrons. A molecule 

 of chlorine contains two atoms of chlorine, each of which con- 

 sists of a nucleus and an atmosphere of 17 electrons. Since 

 the chlorine atom is univalent, just as the hydrogen is, there 

 must be one valency electron present in each atom of chlorine 

 whose special function it is to keep the two atoms joined 

 together in the chlorine molecule. That is, we think of a 

 chlorine molecule as consisting of two nuclei, each nucleus 

 surrounded by rings of electrons, 16 electrons in all (situated 

 relatively close to the nucleus), and farther out a ring of two 

 electrons rotating in an orbit just as in the case of the hydro- 

 gen molecule. If now a hydrogen molecule collides with a 

 chlorine molecule, and if there be sufficient displacement of 

 parts produced, it is conceivable that each molecule is broken 

 in such a way that a chlorine nucleus with its attendant 16 

 electrons unites with a hydrogen nucleus by means of the 

 two rotating valency electrons so as to give rise to an un- 

 symmetrical molecule containing one chlorine nucleus with 

 its sixteen electrons rotating close to it, and one hydrogen 

 nucleus with a ring of two electrons rotating perpendicularly 

 to the line joining the nuclei. This new kind of molecule 

 indicates that a chemical reaction has taken place between 

 the hydrogen gas and the chlorine gas with the production of 

 a new substance, hydrochloric acid. 



This single example may serve to show that chemical 

 change involves a rearrangement of electrons and nuclei. At 

 the present time, however, we are not in a position to follow 

 this line of treatment of the mechanism of chemical change 

 in general, for the simple reason that very considerable doubt 

 exists as to the mode of distribution of the electrons in a 

 single atom of fairly high atomic weight, a state of affairs which 

 obviously prevents us attempting the more complex problem 

 of electronic arrangements inside molecules containing several 

 atoms. 



Without attempting to account for the position and mode 



