THE ELECTRON 



91 



TABLE I 



THE ELEMENTS, THEIR ATOMIC NUMBERS, ATOMIC WEIGHTS, AND 

 POSITIONS IN THE PERIODIC SERIES 



The atomic number appears at the left of the symbol for each element, the atomic 

 weight below ; where the latter are not in the order of the atomic numbers they are in italics. 



1 H 



1.008 



NOTE. Each vertical column forms a "group" the elements of which have the valencies 

 indicated by the Roman numerals or else form similar compounds with other elements like 

 hydrogen and oxygen. Each row is a "period." Corresponding to the atomic number 58 

 is the rare metallic element cerium. For simplicity an entire period of rare earths, follow- 

 ing cerium, is omitted from the table of positions although they are included in the list of 

 elements. 



THE LIST OF ELEMENTS IN THE ORDER or ATOMIC NUMBERS: 



