﻿STRUCTURE 
  OF 
  MATTER 
  — 
  COMPTON. 
  

  

  151 
  

  

  which 
  contains 
  only 
  a 
  few 
  examples. 
  Those 
  elements 
  bracketed 
  to- 
  

   gether 
  are 
  isotopes. 
  

  

  Element. 
  

  

  Hydrogen 
  . 
  

   Helium.... 
  

  

  Lithium. 
  

  

  Atomic 
  

   number. 
  

  

  Boron 
  . 
  

  

  Carbon 
  . 
  . 
  

   Nitrogen. 
  

   Oxygen 
  . 
  . 
  

  

  Neon. 
  

  

  Mercury. 
  

  

  Atomic 
  

   weight. 
  

  

  go 
  

  

  1.007 
  

   4 
  

   6 
  

   7 
  

   10 
  

   11 
  

   12 
  

  

  14.01 
  

   16 
  

   20 
  

   21 
  

   22 
  

   197 
  

   198 
  

   199 
  

   200 
  

   202 
  

   204 
  

  

  + 
  Elec- 
  

   trons 
  in 
  

   nucleus. 
  

  

  1 
  

   4 
  

   6 
  

   7 
  

   10 
  

   11 
  

   12 
  

   14 
  

   16 
  

   20 
  

   21 
  

   22 
  

   197 
  

   188 
  

   199 
  

   200 
  

  

  202 
  

   204 
  

  

  - 
  Elec- 
  

   trons 
  in 
  

   nucleus. 
  

  

  

  

  2 
  

  

  3 
  

  

  4 
  

  

  5 
  

  

  6 
  

  

  6 
  

  

  7 
  

  

  8 
  

  

  10 
  

  

  11 
  

  

  12 
  

  

  117 
  

  

  118 
  

  

  119 
  

  

  \20 
  

  

  122 
  

  

  124 
  

  

  1 
  

  

  2 
  

   3 
  

   3 
  

   6 
  

   5 
  

   6 
  

   7 
  

   8 
  

   10 
  

   10 
  

   10 
  

  

  so 
  

   so 
  

   so 
  

   80 
  

  

  Thus 
  far 
  we 
  may 
  go 
  with 
  considerable 
  certainty 
  in 
  our 
  picture 
  of 
  

   atomic 
  structure. 
  When 
  we 
  endeavor 
  to 
  learn 
  how 
  these 
  electrons 
  

   are 
  arranged, 
  both 
  within 
  and 
  without 
  the 
  nucleus, 
  we 
  must 
  base 
  

   our 
  conclusions 
  on 
  such 
  evidence 
  as 
  we 
  can 
  get 
  from 
  the 
  nature 
  of 
  

   the 
  chemical 
  (electromagnetic) 
  forces 
  between 
  atoms, 
  from 
  the 
  

   ways 
  in 
  which 
  the 
  atoms 
  may 
  be 
  broken 
  up 
  or 
  their 
  parts 
  set 
  into 
  

   vibration, 
  producing 
  light 
  or 
  other 
  radiation, 
  from 
  their 
  behavior 
  

   in 
  electric 
  and 
  magnetic 
  fields, 
  etc. 
  To 
  understand 
  the 
  structure 
  

   fully, 
  we 
  should 
  know 
  all 
  about 
  the 
  forces 
  which 
  hold 
  the 
  parts 
  to- 
  

   gether. 
  In 
  this 
  direction 
  some 
  progress 
  has 
  been 
  made 
  but 
  certain 
  

   phases 
  of 
  the 
  problem 
  are 
  very 
  perplexing. 
  

  

  ELECTRONS 
  AND 
  RADIATION. 
  

   Quantum 
  theory. 
  — 
  Electromagnetic 
  theory 
  leads 
  to 
  the 
  conclusion 
  

   that 
  radiation 
  is 
  produced 
  when 
  an 
  electric 
  charge 
  is 
  accelerated, 
  and 
  

   this 
  conclusion 
  has 
  been 
  amply 
  verified. 
  Yet 
  it 
  appears 
  that, 
  under 
  

   some 
  conditions, 
  electrons 
  are 
  accelerated 
  without 
  producing 
  radia- 
  

   tion. 
  Ordinary 
  dynamical 
  theory 
  leads 
  us 
  to 
  expect 
  that 
  a 
  negative 
  

   electron, 
  rotating 
  or 
  oscillating 
  about 
  a 
  center 
  of 
  force, 
  might 
  rotate 
  

   in 
  an 
  orbit 
  of 
  any 
  radius 
  or 
  oscillate 
  with 
  any 
  amplitude 
  under 
  ap- 
  

   propriate 
  conditions. 
  Yet 
  it 
  appears 
  that 
  only 
  certain 
  particular 
  

   stable 
  motions 
  are 
  possible, 
  those 
  which 
  satisfy 
  the 
  condition 
  

   f 
  p 
  dq=hs, 
  where 
  p 
  is 
  the 
  momentum 
  of 
  the 
  electron, 
  q 
  is 
  its 
  distance 
  

   from 
  some 
  reference 
  point 
  in 
  its 
  path, 
  s 
  is 
  any 
  integer 
  such 
  as 
  

   1, 
  2, 
  3, 
  etc., 
  and 
  A 
  is 
  a 
  universal 
  constant, 
  known 
  as 
  Planck's 
  con- 
  

   stant. 
  We 
  naturally 
  think 
  of 
  radiant 
  energy 
  as 
  being 
  emitted 
  con- 
  

  

  