July 22, 1921] 



SCIENCE 



67 



riods contain series of elements which all have 

 3 or 2 and 3 as their principal valences. The 

 atoms of these elements are therefore incom- 

 plete. The electronegative atoms in such com- 

 pounds, however, are always complete. 



It is of interest to note that as long as 

 atoms are incomplete there seems to be no 

 tendency for them to have an even rather than 

 an odd number of electrons. For example, 

 the following ions all have odd numbers of 

 electrons: Cr+++, Mn++, Fe+++, Co++, and Cu++. 

 This seems to indicate that the remarkable 

 tendency, pointed out by Lewis, for most 

 compounds to contain even numbers of elec- 

 trons is due merely to the relative abundance 

 of complete compounds as compared to incom- 

 plete ones. In other words, the even number 

 of electrons in most compounds results from 

 the tendency of Postulate 1 rather than from 

 any more general tendency for electrons to 

 form pairs. 



Many of the compounds of this class, such 

 as ZnO (zincite), FcjO,, PbS, CuO, etc., 

 show electric conductivity even as solids. 

 This is undoubtedly caused by the relatively 

 large number of electrons in incomplete 

 sheaths. Of course we should not expect all 

 compounds which contain such electrons to 

 show conductivity, for the presence of the 

 electronegative atoms might easily prevent the 

 mobility of these electrons. We need to know 

 much more than we now do about the arrange- 

 ment of the atoms and their electrons in 

 space before we can predict conductivity in 

 particular cases of this kind. 



3. Exceptional Cases. — ^There are some 

 substances or compounds whose structure is 

 not adequately accounted for by the foregoing- 

 analysis. A few examples are: N„ CO, CIST", 

 !N"0. The writer believes these have the single 

 octet structure which he described in his 

 earlier publications. It is probable that acety- 

 lene, C„H„, and the carbide ion C„~ (in 

 CaC,, etc.) have the same kind of structure. 

 Pease has suggested that they may all have a 

 triple bond structure.^ This question merits 

 careful study. 



Another set of compounds that must have 



6 Jour. Amer. Chem. Soc, 43, 991 (1921). 



a special structure are various compounds of 

 boron such as B^H,,. 



Most compounds containing molecules of 

 HjO, ISTHg, etc., are readily accounted for by 

 Postulate 3 but many of these should be con- 

 sidered by methods somewhat different from 

 those developed here. 



In double molecules such as H^O^ (in ice), 

 HjF,, and in compounds such as KHF^, etc., 

 it seems that the hydrogen nuclei instead of 

 forming duplets with electrons in the same 

 atom, form duplets in which the two electrons 

 are in different atoms. The hydrogen nucleus 

 itself thus acts as a bond in such a case. 

 Latimer and Rodebush' have made a some- 

 what similar suggestion in regard to hydrogen 

 nuclei acting as bonds. They consider, how- 

 ever, that the hydrogen nucleus acts on two 

 pairs of electrons: one pair in each of the two 

 atoms. It seems to the writer much more 

 probable that the hydrogen nucleus is no more 

 able to attract four electrons than is the 

 nucleus of other atoms. Since the first layer 

 of electrons in all atoms contains only 2 elec- 

 trons it seems probable that the hydrogen in 

 this case also holds only two electrons and 

 that these form the definite stable group which 

 we have termed the duplet. 



The writer plans to consider the quantitative 

 aspects of these valence theories in subsequent 

 papers. It is aimed to put Postulates 1 and 

 3 into a form that will permit at least rough 

 calculations of the relative stabilities of va- 

 rious substances as measured, for example, by 

 their heats of formation. 



Irving Langmuie 



Eeseakch Laboratory, 



General Electric Company, 

 Schenectady, N. Y., 

 June 29, 1921 



PROFESSOR H. BRUCHMANN 



The men who gave such distinction to 

 botany in Germany during the latter half of 

 the nineteenth century, have mostly gone, the 

 years since 1914 taking heavy toll of those who 

 were left when war broke out. Among the 

 last of the veterans was Professor Bruchmann 



■r Jour. Amer. Chem. Soc, 42, 1431 (1920). 



