rEBRUARY 21, 1919] 



SCIENCE 



181 



genuine valence compounds and not molecular 

 compounds, as Werner supposes them to be. 

 If we assume rotating electrons, as we are 

 almost compelled to do, molecules may well be 

 held together by magnetic attractions and it 

 seems possible that such attractions give rise 

 to the secondary valences of Werner. He and 

 his students have done magnificent work in 

 the study of complex inorganic compounds, 

 and some apparent contradictions between his 

 ideas and those of organic chemists will doubt- 

 less be cleared up in the future. 



To rei)eat, the most important recent ad- 

 vance in the theory of valence has been the 

 interpretation of the theory in connectiou 

 with the electron theory and a beginning to- 

 ward the study of positive and negative atoms 

 in organic compounds. 



It is not very safe to prophesy, but I am 

 impressed with the need of a more definite 

 knowledge of the structiu-e of atoms as a 

 basis for a better understanding of valence. 

 So much progress has been made in this 

 direction during the past twenty years that 

 further advance seems probable. Several differ- 

 ent lines of study may be suggested, the 

 coordination of which might lead to further 

 knowledge. 



The spectra of the elements must be in- 

 timately connected with the structure of the 

 atoms. Professor Morley once suggested that 

 the problem is something like that of a man 

 who should endeavor to determine the mech- 

 anism of a grand piano with only sound waves 

 to guide him. Yet the matter seems by no 

 means hopeless and a beginning has already 

 been made. It is noticeable that spectral 

 lines are only given out by ionized gases and 

 are ix>ssibly connected with the motion of 

 valence electrons. 



Certain forms of structure, especially those 

 forms in which there are what Baeyer so aptly 

 called fliesende doppeUe Bindunge. absorb 

 light of certain wave-lengths and give us 

 colored compoimds. This means that it is 

 possible to calculate exactly the rate at which 

 certain atoms, or parts of atoms, or of mole- 

 cules vibrate. 



The atomic nimibers determined by X-ray 



spectra must be due to some more rapid and 

 very fundamental sort of vibration which 

 changes as the nucleus of the atom increases 

 in weight from one element to another of the 

 periodic system. 



By means of X-rays it has been possible to 

 determine the actual arrangement of atoms 

 in crystals. The conclusion has been drawn 

 from some of this work that the results do not 

 agree with our customary conceptions of va- 

 lence. I am inclined to think that the achieve- 

 ments of organic chemistry are not to be dis- 

 carded so easily. 



The Walden inversion has been interpreted 

 by Fischer and Werner in terms of general 

 attraction between atoms as opposed to local- 

 ized attraction. The subject deserves care- 

 ful study. 



The evidence from radioactive disintegra- 

 tions that helium atoms and electrons form 

 essential parts of some atoms and very prob- 

 ably of all, is certainly important. The spec- 

 ulations of W. D. Harkins in this connection 

 may be mentioned. The enormous quantity 

 of energy liberated by the disintegration of 

 an atom is certainly significant. 



Three suggestions as to the functions of 

 electrons in holding atoms together may be 

 mentioned. One is that one or two electrons 

 rotate about a line joining the centers of two 

 positive nuclei, at a point midway between 

 them. In ionization these electrons must re- 

 main with the negative ion. A second sug- 

 gestion is that the magrnetic effect produced 

 by rotating electrons may cause an attraction 

 between atoms. This is the magneton theory 

 of Parsons and something of the same sort 

 was suggested by Sir William Ramsay in the 

 last paper which he published. It would also 

 accoimt for the non-polar combinations of 

 G. N. Lewis. A third suggestion is that an 

 electron may rotate about positive nuclei 

 situated in two atoms. The velocity of elec- 

 trons must be so much greater than ordinary 

 motions of atoms that the atoms might be 

 kept together in this way. 



Whatever conclusions may finally be reached 

 with regard to the structure of atoms it seems 

 very certain that the structure will be found 



