WYCKOFF: FORCES BETWEEN ATOMS IN SOLIDS 577 



from a rearrangement of the electrons among the interior rings 

 rather than from the addition of electrons to the atom surface. 

 But this assumption, in common with every other yet made 

 regarding the arrangement of the electrons in the eighth-group 

 and rare-earth metals, is not very satisfactory as a description 

 of the real arrangement of the electrons in these atoms. 



The behavior of hydrogen is interesting. In water solution 

 of many of its compounds it behaves as if strongly "electro- 

 positive." This would indicate that it lost an electron with 

 great readiness. But in most of its properties hydrogen acts 

 like an element which holds on to electrons with great tenacity: 

 its salts with weak anions are much less dissociated than the 

 corresponding alkali salts; it occupies a position quite low in 

 the electromotive series table; many of its compounds are vol- 

 atile, and its diatomic molecule is very stable. This apparently 

 anomalous behavior of many hydrogen compounds follows di- 

 rectly from the structure of its atom. As long as hydrogen pos- 

 sesses a single electron, it holds on to it energetically and tends 

 to acquire another to close its fields; if the electron is removed, 

 the only force exerted by the atom is due to the attraction of its 

 single positive charge. 



THE STRUCTURE OF CHEMICAL COMPOUNDS, PARTICULARLY SOLIDS 



Polar and non-polar compounds. — All chemical compounds 

 may be considered as included within the following extremes, 

 compounds the constituent atoms of which are electrically 



1. Charged, 



2. Neutral. 



If the atoms are charged, the compound is "polar;" if neu- 

 tral, it is what is now called a "non-polar" compound.-^ 



In a polar compound the tendency of the electronegative atom 

 to complete a cluster of eight is so much greater than the attrac- 

 tion of the positive nucleus of the electropositive atom for the 

 outside electrons that the electronegative atom is able to remove 

 them completely. 



29 W. C. Bray and G. E- K. Branch. Journ. Amer. Chem. Soc. 35: 1440-1447. 

 1913- 



