JoLY — Radiant Matter. 



77 



U^tANIUM 





Uraniuh X 



spending its relatively enorinous kinetic energy in shaking and disrupting 

 the harmonious balance within tlie opposing atom. It has been suggested 

 that it acquires its own electric charge at an early stage of its encovmters 

 (shortly after quitting the disintegrating atom which gives rise to it), as a 

 result of its aggressiveness, the bombarded atoms retaliating by knocking off 

 two of its electrons. Such a loss of two unit negative charges would account 

 for the double ionic charge wliich it apparently possesses. Although 

 ionization by these rays within solids into which it penetrates must be, to a 

 certain extent, matter of inference, we shall see later the strongest evidence 

 that these rays, indeed, act in this way upon molecules aggregated in the 

 solid state. 



The conditions under which radiant matter comes into existence are set 

 forth in the table of tlie genealogies of the radio- 

 active element. According to the theory put 

 forward by Eutherford and Soddy, a radioactive 

 element spontaneously transforms into another 

 and different element. It is, from internal causes, 

 unstable. A new atom, derived from a preceding 

 one, at the moment of its birth possesses a certain Ionium - 

 " expectation of life." When this period is over, 

 it, in turn, is transformed into another body. This Radium ■ 

 " expectation of life," or average longevity, is an 

 important distinguishing feature of the several 

 substances. Some, on tlie average, live a long 

 time ; some only a short time. Uranium possesses 

 an expectation of life of about 9000 million years. 

 Radium A endures on the average but 4'3 minutes. 

 It follows that in tlie case of the longer-lived bodies 

 only a very small portion of the total number of 

 atoms present transform each second ; in the case 

 of the shorter-lived bodies the fraction is rela- 

 tively large. 



It will be evident that if a quantity of a parent 

 substance — say, uranium — has been for a long 

 time (some thousands of years) in the rocks, it 

 must accumulate all the several descendants to 

 which it gives rise. These, however, will not 



accumulate in indefinitely large amounts, for, with the exception of the 

 final stable substance, they are being transformed as well as formed. There 

 will be a certain amount of any one particular element (on which we fix 







ZMANATION- 



Radium A—*'^ 



Half Period . 

 6x10 years 



24-6 days. 



Sx/Oyearj- 



2x10 years. 



3 '85 days 



3 minuses. 



Radium B-* P 26'7minutes. 



Radium C^H 

 ^7 



Radium D 



tS-Sminutes. 



15 years. 



Radium £-> /? 4-8 days. 



Radium F- 



(Polonium.) 



• a MOdays. 



