﻿THE 
  

   LONDON, 
  EDINBURGH, 
  and 
  DUBLIN 
  

  

  PHILOSOPHICAL 
  MAGAZINE 
  

  

  AND 
  

  

  JOURNAL 
  OF 
  SCIENCE. 
  

  

  [SIXTH 
  SERIES.] 
  

  

  JUL 
  Y 
  1913. 
  

  

  y 
  ', 
  

  

  

  I. 
  On 
  the 
  Constitution 
  of 
  Atoms 
  and 
  Molecules, 
  

   By 
  N. 
  Bohr, 
  Dr. 
  phil. 
  Copenhagen*. 
  

  

  Introduction. 
  

  

  IN 
  order 
  to 
  explain 
  the 
  results 
  of 
  experiments 
  on 
  scattering 
  

   of 
  a 
  rays 
  by 
  matter 
  Prof. 
  Rutherford 
  f 
  has 
  given 
  a 
  

   theory 
  of 
  the 
  structure 
  of 
  atoms. 
  According 
  to 
  this 
  theory, 
  

   the 
  atoms 
  consist 
  of 
  a 
  positively 
  charged 
  nucleus 
  surrounded 
  

   by 
  a 
  system 
  of 
  electrons 
  kept 
  together 
  by 
  attractive 
  forces 
  

   from 
  the 
  nucleus; 
  the 
  total 
  negative 
  charge 
  of 
  the 
  electrons 
  

   is 
  equal 
  to 
  the 
  positive 
  charge 
  of 
  the 
  nucleus. 
  Further, 
  the 
  

   nucleus 
  is 
  assumed 
  to 
  be 
  the 
  seat 
  of 
  the 
  essential 
  part 
  of 
  

   the 
  mass 
  of 
  the 
  atom, 
  and 
  to 
  have 
  linear 
  dimensions 
  ex- 
  

   CCBdingly 
  small 
  compared 
  with 
  the 
  linear 
  dimensions 
  of 
  the 
  

   whole 
  atom. 
  The 
  number 
  of 
  electrons 
  in 
  an 
  atom 
  is 
  deduced 
  

   to 
  be 
  approximately 
  equal 
  to 
  half 
  the 
  atomic 
  weight. 
  Great 
  

   interest 
  is 
  to 
  be 
  attributed 
  to 
  this 
  atom-model 
  ; 
  for, 
  as 
  

   Rutherford 
  has 
  shown, 
  the 
  assumption 
  of 
  the 
  existence 
  of 
  

   nuclei, 
  as 
  those 
  in 
  question, 
  seems 
  to 
  be 
  necessary 
  in 
  order 
  

   to 
  account 
  for 
  the 
  results 
  of 
  the 
  experiments 
  on 
  large 
  angle 
  

   scattering 
  of 
  the 
  a 
  rays 
  J. 
  

  

  In 
  an 
  attempt 
  to 
  explain 
  some 
  of 
  the 
  properties 
  of 
  matter 
  

   on 
  the 
  basis 
  of 
  this 
  atom-model 
  we 
  meet, 
  however, 
  with 
  

   difficulties 
  of 
  a 
  serious 
  nature 
  arising 
  from 
  the 
  apparent 
  

  

  * 
  Communicated 
  bv 
  Prof. 
  E. 
  Rutherford, 
  F.R.S. 
  

  

  t 
  E. 
  Rutherford, 
  Phil. 
  Mag. 
  xxi. 
  p. 
  669 
  (1911). 
  

  

  X 
  See 
  also 
  Geiger 
  and 
  Marsden, 
  Phil. 
  Mag. 
  April 
  1913. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  151. 
  July 
  1913, 
  ' 
  B 
  

  

  