IONIZATION 195 



dissolve many electrolytes to give solutions of excellent con- 

 ducting power. Water, however, is the solvent most commonly 

 used in chemical operations, and other ionizing solvents need 

 not be considered at this stage. 



/ions and Electrons. The question may be asked : Whence 

 do the ions obtain their electric charges? A brief answer to this 

 question may be attempted here, although for a clear realization 

 of its significance a knowledge of the subject-matter of the final 

 chapter (pp. 552^) is necessary. 



Matter is electrical in its ultimate nature, and the atoms of 

 all elements arejmorejir less complex aggregates_oi positiYfi_and 

 negative electrical units. The positive units (protons') constitute 

 the main mass of the core or nucleus of the atom, and are fixed 

 therein, except in radioactive disintegrations. The outermost shell 

 of the atom consists of a number of negative units (electrons}, which 

 are less rigidly held. The atom as a whole, of course, is electrically 

 neutral. The hydrogen atom, to choose the simplest example, is 

 made up of a single proton and a single electron. The structure 

 of the atoms of other elements is, of course, more complex, but 

 all possess, in their outermost shell, a definite small number of 

 electrons, which are relatively loosely held. When two atoms of 

 different elements combine, it may happen that an electron (or 

 a number of electrons) will pass from one atom to the other. 

 Atoms which lose electrons in this way become positive radicals, 

 the departure of an electron leaving the atom as a whole elec- 

 trically positive. Atoms which gain electrons become negative 

 radicals, arrival of an electron making the atom as a whole elec- 

 trically negative. Under normal circumstances, the attractive 

 forces between such oppositely-charged radicals will be sufficient, 

 in most cases, to bind them firmly together as electrically neutral 

 molecules. If we weaken these forces, however, as we undoubtedly 

 do when we dissolve an electrolyte in a solvent such as water, 

 separation of the bound radicals into free positive and negative ions 



