﻿THE 
  

  

  LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  : 
  

  

  [SIXTH 
  SERIES.] 
  

  

  APRIL 
  1918. 
  

  

  \ 
  

  

  XXXV. 
  Ihe 
  X-Ray 
  Spectra 
  and 
  the 
  Constitution 
  of 
  the 
  Atom, 
  

   By 
  L. 
  Vegard, 
  Dr. 
  phil. 
  University 
  Christiania 
  *. 
  

  

  § 
  1. 
  A 
  OCORDING 
  to 
  Rutherford 
  f 
  the 
  atom 
  consists 
  

   J\. 
  of 
  a 
  positive 
  nucleus 
  and 
  electrons 
  circulating 
  

   round 
  it. 
  A 
  number 
  of 
  different 
  methods 
  have 
  led 
  to 
  the 
  

   result 
  that 
  the 
  number 
  of 
  electrons 
  in 
  the 
  neutral 
  atom 
  is 
  

   equal 
  to 
  the 
  atomic 
  number 
  N, 
  and 
  that 
  consequently 
  the 
  

   charge 
  of 
  the 
  nucleus 
  is 
  4-Ne. 
  The 
  stability 
  of 
  the 
  system 
  

   is 
  not 
  secured 
  by 
  the 
  usual 
  electrodynamic 
  forces, 
  but 
  

   Bohr 
  X 
  by 
  his 
  ingenious 
  explanation 
  of 
  the 
  series 
  spectra 
  

   has 
  been 
  able 
  to 
  fix 
  orbits 
  of 
  stability 
  by 
  means 
  of 
  the 
  

   energy 
  quanta 
  introduced 
  by 
  Planck. 
  

  

  The 
  fundamental 
  assumptions 
  underlying 
  Bohr's 
  theory 
  of 
  

   atoms 
  and 
  their 
  light 
  emission 
  are 
  the 
  following 
  : 
  — 
  

  

  I. 
  In 
  the 
  normal 
  state 
  of 
  the 
  atom 
  the 
  electrons 
  are 
  

   arranged 
  in 
  groups 
  (rings) 
  in 
  such 
  a 
  way 
  that 
  for 
  each 
  

  

  electron 
  the 
  angular 
  momentum 
  is 
  equal 
  to 
  ^r— 
  or 
  

  

  mcoa 
  2 
  = 
  — 
  , 
  . 
  . 
  . 
  . 
  . 
  . 
  (la) 
  

  

  where 
  m 
  is 
  the 
  mass, 
  a> 
  the 
  angular 
  velocity 
  of 
  the 
  electron, 
  

   a 
  the 
  radius 
  of 
  the 
  circular 
  orbit, 
  and 
  h 
  Planck's 
  constant. 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  The 
  results 
  of 
  the 
  present 
  investi- 
  

   gation 
  were 
  communicated 
  to 
  the 
  Kristiania 
  Vid. 
  Selsk. 
  on 
  October 
  23 
  

   and 
  30, 
  and 
  read 
  before 
  the 
  Society 
  November 
  23. 
  

  

  f 
  E. 
  Rutherford, 
  Phil. 
  Mag. 
  xxi. 
  p. 
  669 
  (1911), 
  and 
  xxviii. 
  p. 
  488 
  

   (1914). 
  

  

  X 
  N. 
  Bohr, 
  Phil. 
  Mag. 
  xxvi. 
  pp. 
  1, 
  476, 
  857 
  (1913). 
  

  

  Phil. 
  Mag, 
  S. 
  6. 
  Vol. 
  35. 
  No. 
  208. 
  April 
  1918. 
  Y 
  

  

  