/iiiiiiiiiiiiiiimmnitiii 



THE ATOM 103 



The three most abundant elements, oxygen, iron, 

 and calcium, have even atomic number. (That the 

 most abundant elements are of even atomic number, 

 was first pointed out by Harkins, 1917.) 



All the elements found in organisms in large 

 amounts are some of the lighter elements. Most 

 of them belong to the two small periods of eight 

 elements each, the exceptions being hydrogen (first 

 period of two, or standing alone), and potassium, 

 calcium, and iron (fourth period of eighteen). 



According to the research of Aston, hydrogen, 

 carbon, nitrogen, oxygen, sodium, phosphorus, and 

 sulphur are simple elements. The rest are isotopes. 



Sodium, potassium, magnesium, calcium, and 

 carbon are electropositive; nitrogen, phosphorus, 

 oxygen, sulphur, and chlorine, electronegative. Po- 

 tassium shows weak radioactivity. 



Carbon and nitrogen are among the elements that 

 have been stripped of their outer electrons by Milli- 

 kan. 



Nitrogen, sodium, and phosphorus have been 

 shattered by Rutherford. 



Nitrogen, it is well known, is very important to 

 life, although it does not support combustion; and it 

 is especially interesting that the product of nitrogen 

 shattered (with the loss of two hydrogen nuclei) 

 would be carbon. 



