ARE THE ELEMENTS TRAN SMUT ABLE? 45 



These products appear to be elements, and this idea that some ele- 

 ments may have existences of but short duration, from a few seconds 

 to many years, is a decidedly novel one. It has been suggested that 

 this may account for some of the vacant spaces in our periodic table 

 of the elements, particularly in the neighborhood of thorium, radium 

 and uranium. Perhaps these spaces never will be occupied except by 

 transients. Indeed it is not impossible that all our elements are mere 

 transients, mere conditions of things, all undergoing change. But 

 there is no immediate danger of their all vanishing away in the form 

 of rays and emanations. Rutherford has calculated that radium will 

 be half transformed in about 1,300 years, that uranium will be half 

 transformed in 6 X 10 s years, and thorium in about 2.4 X 10 9 years. 

 ■We may safely say the other elements are decaying much more slowly, 

 so we may continue to direct our anxieties towards the probable dura- 

 tion of our coal beds and deposits of iron ore as matters of more present 

 concern. 



The objection may be raised that perhaps radium should not be 

 classed as an element, but rather should be considered as an unstable 

 compound in the act of breaking down into its elements. But the 

 answer to this objection is at hand. The evolution of energy accom- 

 panying these changes is far in excess of that obtainable from any 

 known chemical process, so far in excess that it is certain we are deal- 

 ing with a source of energy hitherto unknown to us, with a wholly 

 new class of phenomena. The following quotation from Whetham 6 will 

 convey an adequate conception of the magnitude of the forces at work 

 here : 



It is possible to determine the mass and the velocity of the projected 

 particles, and. therefore, to calculate their kinetic energy. From the prin- 

 ciples of the molecular theory, we know that the number of atoms in a gram 

 of a solid material is about 10 20 . Four or five successive stages in the dis- 

 integration of radium have been recognized, and, on the assumption that each 

 of these involves the emission of only one particle, the total energy of radia- 

 tion which one gram of radium could furnish if entirely disintegrated seems 

 to be enough to raise the temperature of 10 s grams, or about 100 tons, of 

 water through one degree centigrade. This is an underestimate ; it is possible 

 that it should be increased ten or a hundred times. As a mean value, we may 

 say that, in mechanical units, the energy available for radiation in one ounce 

 of radium is sufficient to raise a weight of something like ten thousand tons 

 one mile high. 



Again, 



the energy liberated by a given amount of radioactive change ... is at 

 least 500,000 times, and may be 10,000,000 times, greater than that involved in 

 the most energetic chemical action known. 



The theory that the source of most of the sun's energy is a decay 

 of elements analogous to radium, to disintegration of atoms, is acknowl- 

 edged to account better than any previous theory for the great quantity 



6 ' The Recent Development of Physical Science,' W. C. D. Whetham. 



