76 WHAT IS LIFE 



Concerning the elements, the basic and rudimental 

 concepts are definite and simple. 



1. The atoms of the elements are built up of 

 positively charged nuclei and electrons. 



2. The elements form a definite and limited series. 

 It is now well known (especially because of Henry 

 Moseley*s work) that the elements form a series 

 from hydrogen, atomic number 1, to uranium, 

 atomic number 92. This series is one of simple 

 arithmetical progression, and represents the basic 

 classification of the elements. The atomic number 

 (as was suggested by Van den Broek^) is determined 

 by the number of free positive unit charges on the 

 nucleus of the atom, every succeeding element add- 

 ing one unit to its number of charges. 



Not atomic weight, arbitrarily on the basis of 

 oxygen=16, which gives hydrogen =1.0077, he- 

 lium =4, to uranium = 238.2, but atomic number 

 gives the truly basic conception of the progression 

 of the atoms in the natural system of the elements- 

 In the lighter atoms, that is from helium, atomic 

 number 2, atomic weight 4, to calcium, atomic 

 number 20, atomic weight 40.07, half of the atomic 

 weight about equals the atomic number. From cal- 

 cium on to uranium, atomic number 92, atomic 

 weight, 238.2, there is increasing disparity between 

 atomic number and atomic weight. 



1 PkysikaliKchr Zeii.tnhriff. XIV, 33, 1913. 



