52 THE ROYAL SOCIETY OF CANADA 



with the arrangement of the extra-nuclear electrons, or possibly with 

 the arrangement of the electrons in the outer ring or shell, which are 

 the valence electrons. 



As a result of these general observations regarding the dis- 

 tribution of the paramagnetic and diamagnetic properties among 

 the elements of the periodic system, it is possible to make some pre- 

 dictions of the magnetic properties of the elements which have not 

 yet been examined. For instance, it is to be expected that the 

 elements. Scandium, Yttrium and Lanthanum on the left-hand side 

 of Group III will prove to be paramagnetic and that the other inert 

 gases. Neon, Krypton, Xenon and Niton will be strongly diamagnetic. 

 It will be of some interest to discover just what are the magnetic 

 properties of these elements. 



A remarkable variation is shown in the magnetic susceptibilities 

 of the elements of the first long period, starting with Potassium, as the 

 atomic number increases. Potassium is slightly paramagnetic and 

 the paramagnetism increases steadily through the elements Calcium, 

 Titanium, Vanadium, Chromium and Manganese till it reaches its 

 maximum in the so-called ferromagnetic elements, Iron, Cobalt and 

 Nickel. There is then an abrupt change to diamagnetic properties 

 in all the remaining elements in the period up to Krypton. This 

 peculiarity is repeated in both the next two long periods and is an 

 important point in testing theories of atomic structure. Langmuir^ 

 has discussed these breaks in magnetic properties in connection with 

 his extension of Lewis' theory of atomic structure and has shown that 

 they are incorporated in a qualitative way at least in his model. 



Another way of presenting the variation of the magnetic pro- 

 perties of the chemical elements is shown in Fig. 1, which is the well- 

 known atomic volume curve obtained by plotting atomic numbers as 

 abscissae and atomic volumes as ordinates, the latter being defined 

 as the ratio of the atomic weight to the density of the element con- 

 cerned. On the line below the curve the magnetic properties of the 

 elements have been indicated by a plus sign or a minus sign directly 

 below the element concerned, where these signs denote para- and dia- 

 magnetism respectively. It will be seen that for all elements of atomic 

 number greater than 10, that is, for sodium and all the heavier ele- 

 ments, there is a quite distinct distribution of the paramagnetic and 

 diamagnetic elements along the curve. The paramagnetic elements 

 without exception occur on the descending slopes of the peaks. 

 Thus, from Sodium to Aluminium inclusive, from Potassium to 



^Am. Chem. Soc, J. 41, pp. 868-934, June, 1919. 



