58 SCIENCE PROGRESS 



which 2 each go to complete the first shells, leaving lo over. 

 In view of the stability of the octet, it seems reasonable to 

 suppose that 8 of these electrons arrange themselves in one 

 octet around two nuclei, leaving 2 extra electrons imprisoned 

 somewhere within, held by the attraction of the 14 positive 

 charges. Indeed, there seem to be a number of exceptional 

 factors which tend to produce this result. The S free electrons 

 in each atom cannot form two octets without sharing 3 

 electrons. This does not seem to be a stable grouping in the 

 case of nitrogen. Nor can three atoms form a molecule, since 

 this would give an odd number of electrons. Actually, there 

 are only 2 electrons more than are required to form a single 

 octet round two kernels of small volume and large positive 

 charges. This structure explains satisfactorily the remarkable 

 qualities of nitrogen, the great number of endothermic com- 

 pounds it forms, the inertness of the nitrogen molecule, and the 

 activity of the element in combination. 



The structure of carbon monoxide has long been a puzzling 

 problem. According to the usual view carbon should be 

 divalent in this compound and very much unsaturated. On 

 the contrary, it is a relatively inactive substance. Its very 

 low boiling-point indicates little external field, which is con- 

 firmed by its small solubility in water and the few substances 

 with which it combines at ordinary temperatures. If we apply 

 the octet theory, and suppose w = 2 for the two atoms, we 

 have e = 10, which gives p = Z- Again, this result would 

 indicate a very unsaturated compound. Here also we have 

 a total of 14 electrons in the outer shell, around two nuclei, 

 one with 6 positive charges and the other with 8, or 14 positive 

 charges in all. This at once suggests that the arrangement 

 may be similar to that of the nitrogen molecule. The pro- 

 perties of carbon monoxide should therefore be co-ordinate 

 with those of nitrogen. These are tabulated for comparison 

 below : 



Freezing-point . 

 Boiling-point 

 Critical temperature . 

 Critical pressure. 

 Critical volume . 

 SolubUity in H,0 at 0° C. 

 Density at boiling-point 

 Viscosity at 0° C. 



ndicate an analogous arrangement 



Similar considerations 

 for the nitric oxide molecule. It has 1 5 electrons, only one 

 more than nitrogen and carbon monoxide, and the remarkable 

 paramagnetic properties of nitric oxide may be due to this 

 extra electron. 



