ELECTRON THEORY KLOEFFLER 245 



the nuclei of other atoms as their parent. At that instant the urge 

 resulting from a difference of potential can easily move these free 

 electrons along the circuit. 



The passage of an electric current through a liquid is easily under- 

 stood on the basis of the electron theory. Distilled water is practically 

 an insulator but when an acid or base is added to the water it becomes 

 a conductor. It appears that part of the molecules of the added 

 material automatically dissociate into fragments or ions. Thus 

 hydrochloric acid separates into H+ and CI— and sodium chloride 

 into Na+ and CI— . This means that the H and Na atoms con- 

 stituting the positive ion have lost one electron and are positively 

 charged. In a similar manner, the CI atom has an additional electron 

 and carries a negative charge. If a difference of potential is applied 

 to electrodes in the solution, the negative ions will travel to the 

 positive electrode and give up an electron. In like manner, the 

 positive ion will travel to the negative electrode and take on an 

 electron. Thus the ions serve as carriers to convey electrons through 

 the solution and this movement of electrons constitutes the electric 

 current. 



CURRENT FLOW IN GASES 



Conduction of electricity through gases is produced through the 

 medium of ions as in a liquid but the ions are produced in a different 

 manner. Gas ions may result from the bombardment of gas atoms 

 by high-speed electrons or ions, and by the action of electromagnetic 

 waves of suitable frequency. If a high-speed electron is projected into 

 a gas, it will collide with some of the molecules of that gas. The 

 collision usually occurs with the electrons in the outer orbits of gas 

 atoms. The result may be merely the change of direction of the 

 flying electron or it may be the actul removal of an electron from the 

 outer orbit of the gas atom. When the disruption of the atom takes 

 place, the remaining part of the atom has lost an electron, is positively 

 charged, and is called a positive ion. The electron which is removed 

 may remain a free electron and as such it is a negative ion. It may 

 join another neutral atom and thus form a negative ion of a different 

 kind as far as mass is concerned. 



The two gas ions formed by the bombardment of a single electron 

 will move to electrodes having a difference of potential and placed 

 within that gas. In transit to the electrodes these gas ions will collide 

 with other gas molecules and if the difference of potential is sufficiently 

 high and other conditions favorable, these collisions will result in the 

 production of other gas ions. The latter ions may likewise produce 

 still others while in transit to their respective electrodes. Thus 

 ionization of a gas becomes somewhat accumulative in action and 

 fairly large currents may result. 



