﻿500 
  Dr. 
  N. 
  Bohr 
  on 
  the 
  Constitution 
  

  

  remarkable 
  homogeneity 
  of 
  the 
  characteristic 
  Rontgen 
  

   radiation— 
  indicated 
  by 
  experiment's 
  on 
  absorption 
  of 
  the 
  

   rays, 
  as 
  well 
  as 
  by 
  the 
  interference 
  observed 
  in 
  recent 
  

   experiments 
  on 
  diffraction 
  of 
  Rontgen 
  rays 
  in 
  crystals 
  — 
  is 
  

   in 
  agreement 
  with 
  the 
  main 
  assumption 
  used 
  in 
  Part 
  I. 
  (see 
  

   p. 
  7) 
  in 
  considering 
  the 
  emission 
  of 
  line-spectra, 
  viz. 
  that 
  the 
  

   radiation 
  emitted 
  during 
  the 
  passing 
  of 
  the 
  systems 
  between 
  

   different 
  stationary 
  states 
  is 
  homogeneous. 
  

  

  Putting 
  in 
  (4) 
  F 
  = 
  N, 
  we 
  get 
  for 
  the 
  diameter 
  of 
  the 
  

  

  innermost 
  ring 
  approximately 
  2a 
  = 
  ^ 
  . 
  10 
  -8 
  cm. 
  For 
  

  

  N 
  = 
  100 
  this 
  gives 
  2a 
  = 
  10~ 
  10 
  cm., 
  a 
  value 
  which 
  is 
  very 
  

   small 
  in 
  comparison 
  with 
  ordinary 
  atomic 
  dimensions 
  but 
  

   still 
  very 
  great 
  compared 
  with 
  the 
  dimensions 
  to 
  be 
  expected 
  

   for 
  the 
  nucleus. 
  According 
  to 
  Rutherford's 
  calculation 
  the 
  

   dimensions 
  of 
  the 
  latter 
  are 
  of 
  the 
  same 
  order 
  of 
  magnitude 
  as 
  

   10- 
  12 
  cm. 
  

  

  § 
  6. 
  Radioactive 
  Phenomena. 
  

  

  According 
  to 
  the 
  present 
  theory 
  the 
  cluster 
  of 
  electrons 
  

   surrounding 
  the 
  nucleus 
  is 
  formed 
  with 
  emission 
  of 
  energy, 
  

   and 
  the 
  configuration 
  is 
  determined 
  by 
  the 
  condition 
  that 
  

   the 
  energy 
  emitted 
  is 
  a 
  maximum. 
  The 
  stability 
  involved 
  by 
  

   these 
  assumptions 
  seems 
  to 
  be 
  in 
  agreement 
  with 
  the 
  general 
  

   properties 
  of 
  matter. 
  It 
  is, 
  however, 
  in 
  striking 
  opposition 
  

   to 
  the 
  phenomena 
  of 
  radioactivity, 
  and 
  according 
  to 
  the 
  

   theory 
  the 
  origin 
  of 
  the 
  latter 
  phenomena 
  may 
  therefore 
  be 
  

   sought 
  elsewhere 
  than 
  in 
  the 
  electronic 
  distribution 
  round 
  

   the 
  nucleus. 
  

  

  A 
  necessary 
  consequence 
  of 
  Rutherford's 
  theory 
  of 
  the 
  

   structure 
  of 
  atoms 
  is 
  that 
  the 
  a-particles 
  have 
  their 
  origin 
  

   in 
  the 
  nucleus. 
  On 
  the 
  present 
  theory 
  it 
  seems 
  also 
  neces- 
  

   sary 
  that 
  the 
  nucleus 
  is 
  the 
  seat 
  of 
  the 
  expulsion 
  of 
  the 
  

   high-speed 
  /3-particles. 
  In 
  the 
  first 
  place, 
  the 
  spontaneous 
  

   expulsion 
  of 
  a 
  /3-particle 
  from 
  the 
  cluster 
  of 
  electrons 
  sur- 
  

   rounding 
  the 
  nucleus 
  would 
  be 
  something 
  quite 
  foreign 
  to 
  

   the 
  assumed 
  properties 
  of 
  the 
  system. 
  Further, 
  the 
  expul- 
  

   sion 
  of 
  an 
  a-particle 
  can 
  hardly 
  be 
  expected 
  to 
  produce 
  a 
  

   lasting 
  effect 
  on 
  the 
  stability 
  of 
  the 
  cluster 
  of 
  electrons. 
  The 
  

   effect 
  of 
  the 
  expulsion 
  will 
  be 
  of 
  two 
  different 
  kinds. 
  Partly 
  

   the 
  particle 
  may 
  collide 
  with 
  the 
  bound 
  electrons 
  during 
  its 
  

   passing 
  through 
  the 
  atom. 
  This 
  effect 
  will 
  be 
  analogous 
  to 
  

   that 
  produced 
  by 
  bombardment 
  of 
  atoms 
  of 
  other 
  substances 
  

   by 
  a-rays 
  and 
  cannot 
  be 
  expected 
  to 
  give 
  rise 
  to 
  a 
  subsequent 
  

   expulsion 
  of 
  /3-rays. 
  Partly 
  the 
  expulsion 
  of 
  the 
  particle 
  

  

  