lis BRLL SYSTEM TECHNICAL JOURNAL 



dear. The (iiar.irter of the M.uIT spectrum teaches soniethin^q; about 

 the Ki'oi'I), ^■iz■, that its ele\enth electron inoNcs in a 3i orbit. If these 

 two groups are just tiie s.inu-, then the two independently acquired 

 facts about them ma\- be united into a precious correlation. As a 

 matter of fact it is generally assumed that they are nearly if not quite 

 the same. A valuable piece of evidence bearing upon precisely this 

 point, although relating to a ditTerent element, was described in the 

 foregoing section. 



This suggests that it would be a most desirable achievement to 

 produce the spectra due to groups of (Z — b) electrons congregated 

 about a nucleus of charge +Ze, for some value of Z (the higher the 

 better) and all values of b from to (Z-1). Were this done we 

 could almost lay claim to having witnessed the creation of an atom 

 from fundamental particles common to all matter. We could not 

 quite make this claim, since the nucleus of charge -\-Ze would still 

 remain characteristic of that one kind of atom alone; but we should 

 have made a substantial approach to it. However, there is no im- 

 mediate prospect of achieving this except for the cases Z =^ 1 and 

 Z = 2 which have already been considered. Our inability to produce 

 the spectrum expected for L«++ (i.e. for Z = 3 and ^ = 2) acts as a 

 barrier against utterly tearing down the electron-structures of higher 

 atoms so that they can rebuild themselves before our eyes from the 

 foundations. 



The next important question may be introduced in this fashion. 

 Suppose that nothing were known about the spectrum called Mgll, 

 therefore nothing about the process of adding an eleventh electron 

 to a group of ten around a nucleus of charge 12 e. Knowledge would 

 still be available about the process of adding an eleventh electron to 

 a group of ten about a nucleus of charge lie; for this is precisely 

 the process which creates the neutral sodium atom out of the Na+ion, 

 and results in the emission of the Nal spectrum or arc spectrum of 

 sodium. This spectrum is a doublet spectrum, and it shows that the 

 normal state of the sodium atom is an 5-state, probably of total 

 quantum number 3. This last fact is taken to mean that the eleventh 

 electron in a group of ele\-en electrons about a nucleus of charge 

 + 11 g, is revolving in a 3i orbit. Could we have assumed that there- 

 fore the eleventh electron, in a group of eleven electrons about a 

 nucleus of charge +12 e, is revolving in a 3i orbit? There is no a 

 priori certainty of this: but the observations on the Mgll spectrum, 

 as we have seen, confirm it (and also that the residue of the Mg + ion 

 is like the residue of the Na atom, in causing the next added electron 

 to produce a spectrum of the doublet type). 



