﻿STRUCTURE 
  OF 
  MATTER 
  — 
  COMPTON. 
  155 
  

  

  The. 
  Lewis-Langmuir 
  theory. 
  — 
  In 
  marked 
  contrast 
  with 
  the 
  pre- 
  

   ceding 
  dynamical 
  model 
  of 
  an 
  atom. 
  Professor 
  Lewis 
  and 
  Doctor 
  

   Langmuir 
  have 
  developed 
  a 
  static 
  theory 
  of 
  atomic 
  structure 
  to 
  ac- 
  

   count, 
  primarily, 
  for 
  the 
  chemical 
  valencies 
  of 
  atoms 
  and 
  the 
  periodic 
  

   recurrence 
  of 
  their 
  properties 
  when 
  they 
  are 
  arranged 
  in 
  the 
  order 
  

   of 
  their 
  atomic 
  numbers. 
  In 
  this 
  theory 
  the 
  electrons 
  outside 
  the 
  

   nucleus 
  are 
  arranged 
  as 
  symmetrically 
  as 
  possible 
  in 
  positions 
  on 
  the 
  

   surfaces 
  of 
  imaginary 
  concentric 
  " 
  shells." 
  The 
  maximum 
  possible 
  

   numbers 
  of 
  electrons 
  in 
  these 
  are 
  2 
  in 
  the 
  inmost 
  shell, 
  8 
  in 
  the 
  next, 
  

   8 
  in 
  the 
  next, 
  18 
  in 
  the 
  next, 
  18 
  in 
  the 
  next, 
  etc. 
  No 
  shell 
  can 
  contain 
  

   any 
  electrons 
  unless 
  all 
  the 
  shells 
  inside 
  it 
  contain 
  their 
  full 
  quota 
  of 
  

   electrons. 
  The 
  number 
  of 
  electrons 
  to 
  be 
  thus 
  distributed 
  in 
  the 
  case 
  

   of 
  any 
  given 
  atom 
  is 
  equal 
  to 
  the 
  atomic 
  number 
  of 
  the 
  atom. 
  Chem- 
  

   ical 
  combinations 
  of 
  atoms 
  are 
  supposed 
  to 
  be 
  due 
  to 
  the 
  " 
  sharing 
  " 
  

   of 
  electrons 
  in 
  common 
  by 
  different 
  atoms 
  in 
  such 
  a 
  way 
  as 
  to 
  give 
  

   the 
  outer 
  shells 
  of 
  all 
  the 
  atoms 
  as 
  nearly 
  as 
  possible 
  their 
  full 
  quota 
  

   of 
  electrons. 
  This 
  theory 
  of 
  chemical 
  combination, 
  which 
  we 
  have, 
  

   of 
  necessity, 
  treated 
  very 
  inadequately, 
  is 
  in 
  more 
  complete 
  accord 
  

   with 
  the 
  facts 
  of 
  combination 
  than 
  any 
  other 
  yet 
  proposed. 
  

  

  Discussion. 
  — 
  The 
  chief 
  weaknesses 
  of 
  the 
  Bohr 
  theory 
  are 
  its 
  fail- 
  

   ure 
  to 
  account 
  easily 
  for 
  certain 
  chemical 
  properties 
  and 
  the 
  uncer- 
  

   tainties 
  regarding 
  its 
  proper 
  method 
  of 
  application 
  to 
  any 
  but 
  the 
  

   simplest 
  atoms. 
  The 
  weakness 
  of 
  the 
  Lewis-Langmuir 
  theory, 
  on 
  the 
  

   other 
  hand, 
  lies 
  in 
  its 
  qualitative 
  rather 
  than 
  quantitative 
  nature 
  

   and 
  its 
  disregard 
  of 
  all 
  questions 
  of 
  structural 
  stability, 
  radiation, 
  

   and 
  phenomena 
  due 
  to 
  any 
  part 
  of 
  the 
  atom 
  except 
  the 
  electrons 
  in 
  

   the 
  outer 
  shell. 
  Yet 
  the 
  striking 
  successes 
  of 
  both 
  theories 
  in 
  par- 
  

   ticular 
  fields 
  suggest 
  that 
  both 
  contain 
  elements 
  of 
  truth. 
  The 
  pres- 
  

   ent 
  endeavor 
  is, 
  therefore, 
  to 
  reconcile 
  the 
  two 
  viewpoints, 
  and 
  some 
  

   progress 
  in 
  this 
  line 
  has 
  been 
  achieved. 
  

  

  MATTER, 
  ELECTRICITY, 
  AND 
  ENERGY. 
  

  

  Whenever 
  an 
  electrically 
  charged 
  body 
  is 
  set 
  in 
  motion 
  a 
  magnetic 
  

   field 
  is 
  set 
  up 
  in 
  the 
  region 
  surrounding 
  the 
  body. 
  But 
  a 
  magnetic 
  

   field 
  can 
  not 
  be 
  produced 
  without 
  expending 
  energy, 
  and 
  it 
  is 
  possible 
  

   to 
  calculate 
  how 
  much 
  work 
  must 
  be 
  done 
  to 
  set 
  up 
  any 
  given 
  mag- 
  

   netic 
  field. 
  Obviously, 
  therefore, 
  more 
  work 
  must 
  be 
  done 
  to 
  impart 
  

   a 
  given 
  speed 
  to 
  a 
  body 
  when 
  charged 
  than 
  if 
  it 
  were 
  uncharged. 
  

   In 
  other 
  words, 
  the 
  presence 
  of 
  the 
  charge 
  increases 
  the 
  inertia, 
  or 
  

   mass, 
  of 
  the 
  body. 
  The 
  question 
  immediately 
  suggests 
  itself, 
  there- 
  

   fore, 
  " 
  Is 
  all 
  mass 
  due 
  simply 
  to 
  the 
  electric 
  charges 
  of 
  the 
  positive 
  

   and 
  negative 
  electrons 
  of 
  which 
  matter 
  is 
  composed? 
  " 
  Certain 
  ex- 
  

   periments 
  on 
  the 
  variation 
  of 
  the 
  mass 
  of 
  a 
  negative 
  electron 
  with 
  

   its 
  speed, 
  at 
  speeds 
  approaching 
  the 
  velocity 
  of 
  light, 
  indicate 
  that 
  

   the 
  mass 
  of 
  a 
  negative 
  electron 
  is 
  entirely 
  due 
  to 
  its 
  charge, 
  so 
  that 
  

  

  