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Proceedings of Indiana Academy of Science 



According- to these conceptions of the nature of nitrogen, it can 

 take on three or four hydrogens or organic groups. Langmuir" calls 

 the number of groups that can be added to an atom its covalence. Car- 

 bon, nitrogen and oxygen have the same maximum covalence. The 

 atoms are very nearly the same size as we should expect from their 

 position in the periodic table and, in combination with four groups, 

 they are all probably tetrahedral in shape. This is a modification of 



Fisr. 5. Two possible forms of the steam molecule or monohydrol are given. In one 

 the hydrogens are adjacent ; in the other they are opposite. 



Fig. 6. Dihydrol or liiiuid water must have a condensed form to explain its great 

 density. Three hydrogens are active in connecting two negative oxygens. Note that 

 this aggregate is still polar, one end negative and the other positive. 



the old idea of quinquivalent nitrogen. The polarity of the nitrogen, 

 of course, is diminished according to the length and nature of the organic 

 groups combined with it. 



Oxygen combines with two hydrogens to form a liquid at ordinary 

 temperatures. The oxygen atom with its six electrons in the outer shell 

 completes its octet with the electrons from the two hydrogens. But here 

 there are two pairs of extra electrons corresponding to the single pair 

 of the ammonia molecule. That means that half the molecule is more 



2 Langmuir. J. Am. Chem. Soc, Jtl, 1543 (1919). 



