﻿High-Frequency 
  Spectra 
  of 
  the 
  Elements. 
  1031 
  

  

  v 
  being 
  the 
  frequency 
  of 
  the 
  radiation 
  a, 
  and 
  v 
  the 
  

   fundamental 
  frequency 
  of 
  ordinary 
  line 
  spectra. 
  The 
  latter 
  

  

  is 
  obtained 
  from 
  Rydberg's 
  wave-number, 
  N 
  = 
  — 
  = 
  109,720. 
  

  

  c 
  

  

  The 
  reason 
  for 
  introducing 
  this 
  particular 
  constant 
  will 
  be 
  

  

  given 
  later. 
  It 
  is 
  at 
  once 
  evident 
  that 
  Q 
  increases 
  by 
  a 
  

  

  constant 
  amount 
  as 
  we 
  pass 
  from 
  one 
  element 
  to 
  the 
  next, 
  

  

  using 
  the 
  chemical 
  order 
  of 
  the 
  elements 
  in 
  the 
  periodic 
  

  

  system. 
  Except 
  in 
  the 
  case 
  of 
  nickel 
  and 
  cobalt 
  *, 
  this 
  

  

  is 
  also 
  the 
  order 
  of 
  the 
  atomic 
  weights. 
  While, 
  however, 
  

  

  Q 
  increases 
  uniformly 
  the 
  atomic 
  weights 
  vary 
  in 
  an 
  

  

  apparently 
  arbitrary 
  manner, 
  so 
  that 
  an 
  exception 
  in 
  their 
  

  

  order 
  does 
  not 
  come 
  as 
  a 
  surprise. 
  We 
  have 
  here 
  a 
  proof 
  

  

  that 
  there 
  is 
  in 
  the 
  atom 
  a 
  fundamental 
  quantity, 
  which 
  

  

  increases 
  by 
  regular 
  steps 
  as 
  we 
  pass 
  from 
  one 
  element 
  

  

  to 
  the 
  next. 
  This 
  quantity 
  can 
  only 
  be 
  the 
  charge 
  on 
  the 
  

  

  central 
  positive 
  nucleus, 
  of 
  the 
  existence 
  of 
  which 
  we 
  

  

  already 
  have 
  definite 
  proof. 
  Rutherford 
  has 
  shown, 
  from 
  

  

  the 
  magnitude 
  of 
  the 
  scattering 
  of 
  a 
  particles 
  by 
  matter? 
  

  

  that 
  this 
  nucleus 
  carries 
  a 
  + 
  charge 
  approximately 
  equal 
  to 
  

  

  A. 
  

   that 
  of 
  -~ 
  electrons, 
  where 
  A 
  is 
  the 
  atomic 
  weight. 
  Barkla, 
  

  

  from 
  the 
  scattering 
  of 
  X 
  rays 
  by 
  matter, 
  has 
  shown 
  that 
  the 
  

  

  number 
  of 
  electrons 
  in 
  an 
  atom 
  is 
  roughly 
  — 
  , 
  which 
  for 
  an 
  

  

  electrically 
  neutral 
  atom 
  comes 
  to 
  the 
  same 
  thing. 
  Now 
  

   atomic 
  weights 
  increase 
  on 
  the 
  avernge 
  by 
  about 
  2 
  units 
  at 
  a 
  

   time, 
  and 
  this 
  strongly 
  suggests 
  the 
  view 
  that 
  N 
  increases 
  

   from 
  atom 
  to 
  atom 
  always 
  by 
  a 
  single 
  electronic 
  unit. 
  We 
  

   are 
  therefore 
  led 
  by 
  experiment 
  to 
  the 
  view 
  that 
  N 
  is 
  the 
  

   same 
  as 
  the 
  number 
  of 
  the 
  place 
  occupied 
  by 
  the 
  element 
  in 
  

   the 
  periodic 
  system. 
  This 
  atomic 
  number 
  is 
  then 
  for 
  H 
  1 
  

   for 
  He 
  2 
  for 
  Li 
  3 
  . 
  . 
  . 
  for 
  Ca 
  20 
  . 
  . 
  . 
  for 
  Zn 
  30, 
  &c. 
  This 
  

   theory 
  was 
  originated 
  by 
  Broek 
  t 
  and 
  since 
  used 
  by 
  Bohr 
  %. 
  

   We 
  can 
  confidently 
  predict 
  that 
  in 
  the 
  few 
  cases 
  in 
  which 
  

   the 
  order 
  of 
  the 
  atomic 
  weights 
  A 
  clashes 
  with 
  the 
  chemical 
  

   order 
  of 
  the 
  periodic 
  system, 
  the 
  chemical 
  properties 
  are 
  

   governed 
  by 
  N 
  ; 
  while 
  A 
  is 
  itself 
  probably 
  a 
  complicated 
  

   function 
  of 
  N. 
  The 
  very 
  close 
  similarity 
  between 
  the 
  

   X-ray 
  spectra 
  of 
  the 
  different 
  elements 
  shows 
  that 
  these 
  

   radiations 
  originate 
  inside 
  the 
  atom, 
  and 
  have 
  no 
  direct 
  

   connexion 
  with 
  the 
  complicated 
  light-spectra 
  and 
  chemical 
  

   properties 
  which 
  are 
  governed 
  by 
  the 
  structure 
  of 
  its 
  

   surface. 
  

  

  * 
  Gf. 
  Barkla, 
  Phil. 
  Mag. 
  xiv. 
  p. 
  408 
  (1907). 
  

  

  f 
  Phijs. 
  Zeit. 
  xiv. 
  p. 
  32 
  (1913). 
  % 
  Loc. 
  cit. 
  

  

  