494 



SCIENCE 



[N. S. Vol. XLVI. No. 1195 



regular tetrahedron are arranged around 

 its center. Thus, the tetravalent character 

 of the carbon atom manifests itself clearly. 

 Furthermore, when a model of a diamond 

 crystal is examined, it is discovered that 

 the atoms appear to arrange themselves in 

 rings of six. These relationships suggest 

 at once well known fundamental theories 

 of the organic chemist. 



Through the writings of J. J. Thomson,^ 

 Stark,^ Abegg* and many others, the convic- 

 tion has been reached, that the forces which 

 hold the atoms together, commonly called 

 chemical affinity, are chiefly, if not wholly, 

 electrical in character. The impetus to this 

 interpretation has come from the discov- 

 ery that electricity itself possesses an 

 atomic structure, and that our material 

 atoms appear to be composed of units of 

 positive and negative electrical atoms 

 nicely balanced in the neutral atom. As 

 Carl Barus says :' 



Not only has energy possessed herself of in- 

 ertia, but with ever stronger insistence she is 

 usurping the atomic structure once believed to be 

 among the very insignia of matter. Contempo- 

 raneously matter, itself, the massive, the indestruct- 

 ible, endowed by Lavoisier with a sort of physical 

 immortality, recedes ever more into the back- 

 ground among the shades of velocity and accele- 

 ration. 



Electrochemical theories have not been 

 lacking in the development of chemistry. 

 For many years the electrochemical theory 

 of Berzelius was a guide in the interpreta- 

 tion of chemical phenomena. There is, per- 

 haps, no greater tragedy recorded in the 

 annals of science during the past one hun- 

 dred years than that which overtook Ber- 

 zelius at the close of his active career as 



2 J. J. Thomson, Phil. Mag., March, 1904, 27, 757 

 (1914), etc. 



3 J. Stark, ' ' Die Elektrizitut im Chemischen 

 Atom," Leipzig, 1915. 



*Abegg, Z. Anorg. Chem., 39, 330 (1904); 50, 

 309 (1906). 



5 Science, N. S., Vol. XL., 727, 1914. 



leader of chemical thought. "We of to-day 

 know best why this theory failed, and why 

 we are now busily engaged in formulating 

 a new electrochemical theory, as well as a 

 new electrophysical theory. In fact, J. 

 Stark in his recent work, "Die Elektrizitat 

 im chemischen Atom," gives a eulogy of 

 Berzelius, and points out the many strik- 

 ing qualitative resemblances which the 

 theory of Berzelius bears to his own. 



The special purpose of my remarks to- 

 day precludes any detailed discussion of 

 the various theories concerning the struc- 

 ture of the atom. This phase of the subject 

 has already been presented in the morning 

 meeting of this symposium. It may be 

 said that all theories agree upon a positive 

 core or nucleus associated with negative 

 electrons, the atoms of negative electricity. 

 Thomson presents hypotheses concerning 

 the possible arrangements within the atom, 

 while Stark limits his treatment chiefly to 

 the surface layer. The surface layer, he 

 says, contains an excess of positive electric- 

 ity. In the neutral atom one or more elec- 

 trons, called valence electrons, are held 

 close to the surface of the atom by this posi- 

 tive charge. Compounds are formed, when 

 the lines of force from one or more of these 

 valence electrons reach out and end on the 

 positive areas of other atoms. In the case 

 of strongly polar compounds, an electron 

 is almost wholly drawn over to the atom 

 which it then holds combined. 



Lewis'* classifies compounds into polar 

 and non-polar, but in a footnote remarks: 



It must not be assumed that any one compound 

 corresponds wholly, and at aU times, to any one 

 type. 



He distinguishes between valence num- 

 ber and polar number. Valence number he 

 defines as the number of positions, or re- 

 gions, or points (bond termini) on the 



6G. N. Lewis, J. Am. Chem. Soc, 38, 762 

 (1916). 



