﻿STRUCTURE 
  OF 
  MATTER 
  — 
  OOMPTON. 
  153 
  

  

  Zeeman 
  effect. 
  — 
  Mention 
  only 
  can 
  be 
  made 
  of 
  the 
  discovery 
  by 
  

   Zeeman 
  in 
  189G 
  that, 
  when 
  a 
  source 
  of 
  light 
  is 
  placed 
  in 
  a 
  strong 
  

   magnetic 
  field, 
  its 
  spectral 
  lines 
  are 
  split 
  up 
  into 
  several 
  components. 
  

   The 
  nature 
  of 
  this 
  effect 
  loads 
  to 
  the 
  conclusion 
  that 
  light 
  is 
  emitted 
  

   by 
  negative 
  electrons 
  which, 
  during 
  emission, 
  are 
  moving 
  in 
  orbits 
  

   which 
  are 
  usually 
  circular, 
  but 
  sometimes 
  elliptical. 
  As 
  a 
  matter 
  of 
  

   fact 
  it 
  was 
  the 
  study 
  of 
  the 
  Zeeman 
  effect 
  which 
  first 
  led 
  to 
  the 
  dis- 
  

   covery 
  of 
  the 
  negative 
  electron 
  and 
  to 
  a 
  determination 
  of 
  the 
  ratio 
  of 
  

   its 
  charge 
  to 
  its 
  mass. 
  

  

  Radiation 
  and 
  atomic 
  structure. 
  — 
  A 
  constant 
  correlation 
  of 
  the 
  

   facts 
  of 
  radiation 
  is 
  obtained 
  by 
  supposing 
  that 
  there 
  are 
  only 
  cer- 
  

   tain 
  definite 
  conditions 
  in 
  which 
  it 
  negative, 
  electron 
  may 
  exist 
  in 
  

   Stable 
  equilibrium 
  in 
  an 
  atom, 
  each 
  of 
  these 
  conditions 
  being 
  charac- 
  

   terized 
  by 
  a 
  certain 
  total 
  energy 
  (kinetic 
  plus 
  potential). 
  In 
  the 
  

   case 
  of 
  hydrogen, 
  for 
  example, 
  the 
  energies 
  of 
  all 
  these 
  states 
  arc 
  

   given 
  by 
  — 
  Nh/,s'', 
  where 
  s 
  may 
  have 
  any 
  integral 
  value 
  and 
  each 
  such 
  

   value 
  specifies 
  the 
  energy 
  of 
  an 
  electron 
  in 
  a 
  particular 
  state. 
  When, 
  

   to!- 
  any 
  reason, 
  an 
  electron 
  passes 
  from 
  any 
  state 
  of 
  energy 
  W 
  m 
  to 
  a 
  

   state 
  of 
  less 
  energy 
  W 
  r 
  , 
  the 
  difference 
  between 
  the 
  energies 
  is 
  sent 
  out 
  

   as 
  radiant 
  energy. 
  Thus 
  the 
  energy 
  radiated 
  is 
  W 
  m 
  — 
  W 
  r 
  =Nh 
  

  

  (2" 
  2 
  J" 
  Combining 
  this 
  with 
  the 
  quantum 
  law 
  in 
  form 
  W 
  m 
  - 
  W 
  r 
  = 
  hn, 
  

  

  we 
  have, 
  for 
  the 
  frequency 
  of 
  the 
  resulting 
  radiation, 
  n=M^- 
  .,) 
  

  

  which 
  is 
  the 
  ordinary 
  series 
  formula 
  for 
  hydrogen. 
  Similarly, 
  for 
  

   any 
  element, 
  we 
  interpret 
  the 
  series 
  formula, 
  for 
  any 
  two 
  integral 
  

   values 
  of 
  r 
  and 
  m, 
  as 
  proportional 
  to 
  the 
  difference 
  between 
  the 
  en- 
  

   ergies 
  of 
  an 
  electron 
  in 
  the 
  two 
  corresponding 
  states, 
  and 
  take 
  h 
  to 
  

   be 
  the 
  constant 
  of 
  proportionality. 
  An 
  electron 
  may 
  pass 
  from 
  any 
  

   state 
  to 
  any 
  other 
  state. 
  If 
  the 
  integer 
  characterizing 
  the 
  second 
  

   state 
  is 
  less 
  than 
  that 
  characterizing 
  the 
  first, 
  energy 
  is 
  radiated. 
  If 
  

   the 
  second 
  integer 
  is 
  greater 
  than 
  the 
  first, 
  energy 
  is 
  absorbed 
  by 
  the 
  

   elect 
  1011, 
  from 
  whatever 
  agency 
  produces 
  the 
  displacement. 
  

  

  This, 
  in 
  very 
  bald 
  outline, 
  is 
  the 
  theory 
  of 
  spectral 
  radiation 
  and 
  of 
  

   those 
  features 
  of 
  atomic 
  structure 
  which 
  determine 
  the 
  nature 
  of 
  its 
  

   radiation. 
  When 
  we 
  attempt 
  to 
  account 
  for 
  or 
  describe 
  these 
  partic- 
  

   ular 
  stable 
  states 
  (which 
  really 
  involves 
  accounting 
  for 
  the 
  quantum 
  

   laws) 
  by 
  any 
  dynamical 
  model 
  of 
  an 
  atom, 
  our 
  steps 
  become 
  more 
  

   uncertain, 
  although 
  some 
  notable 
  advances 
  have 
  been 
  made. 
  

  

  ATOMIC 
  MODELS. 
  

  

  The 
  Bohr 
  theory. 
  — 
  Bohr, 
  followed 
  by 
  Sommerfeld 
  and 
  Silber- 
  

   stein, 
  has 
  formed 
  atomic 
  models 
  which 
  have 
  been 
  remarkably 
  suc- 
  

   cessful 
  in 
  accounting 
  for 
  the 
  phenomena 
  of 
  radiation 
  and 
  ionization 
  

   (or 
  breaking 
  up) 
  of 
  systems 
  consisting 
  of 
  a 
  positive 
  nucleus 
  and 
  a 
  

   single 
  outer 
  negative 
  electron, 
  but 
  which 
  have 
  not 
  been 
  developed 
  

  

  