90 SCIENCE REMAKING THE WORLD 



chlorine; and the converse is true of each chlorine atom. 



In the confusion, however, which occurs when salt is 

 dissolved in water the necessity of balancing accounts is 

 momentarily forgotten. The chlorine nucleus moves 

 out into free space between the water molecules, taking 

 with it as an extra satellite an electron from the sodium. 

 The sodium nucleus starts off on its wanderings with 

 one too few electrons. From that time on each is an 

 "ion," an electrically charged particle, seeking a means 

 of balancing its electronic accounts. In its wanderings 

 it may meet with another and oppositely charged ion 

 but the association and consequent satisfaction are only 

 transient because the fluid milieu in which they find 

 themselves encourages incompatibility. (Of course, if 

 there is too little water crystallization occurs.) 



If molecules of some other substance, which also dis- 

 sociates into ions, have been dissolved in the same 

 water these ions may afford satisfaction to the ions 

 formed from the salt. A positive ion, that is one which 

 has lost an electron, will always welcome a meeting with 

 a negative ion for the latter has too many electrons. 



Combinations into molecules occur between atomic 

 systems, that is atoms or ions, either under the urge of 

 attaining greater satisfaction of configuration for the 

 planetary electrons or under the urge of becoming elec- 

 trically neutral. (In the non-chemical phenomena of 

 electricity it is the second urge which is responsible.) 

 The un satisfactions which lead to activities may involve 

 more than one electron for each atom, instead of just 

 one as in the simple case of sodium and chlorine. Com- 

 plicated molecular unions may, therefore, be formed 



