1915'\ Recent Conceptions of the Atom 125 



positive nuclear charge circulate around this as an outer shell. 

 The magnitude of the nuclear positive charge in terms of the 

 hydrogen ion charge is probably the same as the atomic number 

 or number of place occupied by the element in the periodic 

 table. 



Such an atom as that of Eutherford is, as Soddy observes, 

 not stable according to ordinary electro-dynamical laws since 

 there is nothing to prevent the dispersion of the extremely con- 

 centrated central positive charge but, he adds, it is now recog- 

 nized that these laws require modifications. The model has been 

 used with very considerable success in conjunction with Planck's 

 theory of quanta and leads to results in connection, for example, 

 with the series relationships of the hydrogen and helium spec- 

 tra in striking accord with experimental determinations. 



