﻿366 
  Lea 
  — 
  Color 
  Relations 
  of 
  Atoms, 
  Ions 
  and 
  Molecules. 
  

  

  into 
  nine 
  great 
  groups, 
  all 
  absolutely 
  natural, 
  eacli 
  element 
  in 
  

   its 
  proper 
  place 
  accurately 
  iitted. 
  

  

  An 
  examination 
  of 
  Table 
  I 
  will 
  show, 
  

  

  1. 
  Hydrogen 
  stands 
  at 
  the 
  head 
  of 
  the 
  halogen 
  group, 
  with 
  

   the 
  members 
  of 
  which 
  it 
  makes 
  countless 
  substitutions. 
  Hydro- 
  

   gen 
  has 
  always 
  been 
  an 
  element 
  difficult 
  to 
  class, 
  but 
  this 
  is 
  its 
  

   proper 
  place.* 
  

  

  2. 
  Next 
  follows 
  the 
  group 
  of 
  the 
  metals 
  of 
  the 
  alkalies, 
  with 
  

   sodium 
  in 
  its 
  right 
  place. 
  With 
  these, 
  hydrogen 
  is 
  intimately 
  

   connected. 
  

  

  3. 
  The 
  calcium 
  group 
  begins 
  with 
  that 
  metal, 
  either 
  because 
  

   earlier 
  members 
  with 
  lower 
  atomic 
  weights 
  exist, 
  but 
  have 
  not 
  

   been 
  discovered, 
  or 
  because 
  the 
  group 
  naturally 
  commences 
  at 
  a 
  

   later 
  stage 
  than 
  the 
  preceding. 
  The 
  same 
  thing 
  is 
  true 
  with 
  the 
  

   scandium 
  group 
  next 
  following. 
  

  

  4. 
  The 
  remaining 
  groups 
  need 
  no 
  particular 
  description. 
  They 
  

   are 
  eminently 
  natural 
  and 
  very 
  familiar. 
  

  

  5. 
  In 
  these 
  groups 
  following 
  the 
  horizontal 
  lines, 
  all 
  members 
  

   of 
  each 
  group 
  have 
  the 
  same 
  valency. 
  To 
  this 
  there 
  is 
  no 
  excep- 
  

   tion. 
  

  

  The 
  foregoing 
  applies 
  to 
  this 
  table 
  considered 
  as 
  groups 
  

   corresponding 
  to 
  the 
  horizontal 
  lines. 
  When 
  it 
  is 
  intended 
  to 
  

   consider 
  the 
  serial 
  relations 
  according 
  to 
  columns 
  they 
  should 
  

   be 
  taken 
  as 
  one 
  long 
  serial 
  without 
  breaks. 
  

  

  Much 
  importance 
  has 
  naturally 
  been 
  attached 
  by 
  Mendeleef 
  

   to 
  the 
  progressive 
  stages 
  of 
  oxidation 
  in 
  his 
  groups, 
  as 
  for 
  

   example, 
  the 
  series 
  

  

  Na 
  2 
  0, 
  Mg 
  2 
  2 
  , 
  A1 
  2 
  3 
  , 
  Si 
  2 
  4 
  , 
  P 
  2 
  5 
  , 
  S 
  2 
  6 
  , 
  C1 
  2 
  7 
  . 
  

  

  And 
  the 
  corresponding 
  hydroxides, 
  hydrides, 
  methides, 
  etc. 
  

   Of 
  these 
  it 
  may 
  be 
  said 
  that 
  C1 
  2 
  7 
  is 
  purely 
  hypothetical. 
  The 
  

   rest 
  of 
  this 
  series 
  will 
  be 
  found 
  in 
  precisely 
  the 
  same 
  order 
  in 
  

   the 
  second 
  column 
  in 
  Table 
  I 
  and 
  all 
  the 
  corresponding 
  ele- 
  

   ments 
  in 
  each 
  horizontal 
  line 
  have 
  the 
  same 
  valencies 
  and 
  tend 
  

   to 
  form 
  similar 
  compounds. 
  

  

  This 
  table 
  representing 
  the 
  first 
  great 
  divisio?i 
  of 
  elemetits 
  in- 
  

   cludes 
  all 
  those 
  whose 
  ions 
  function 
  as 
  anions 
  with 
  part 
  of 
  the 
  

   kathions. 
  

  

  * 
  By 
  Eoscoe 
  & 
  Schorlemmer 
  and 
  in 
  the 
  Graham 
  Otto 
  treatise 
  ifc 
  is 
  placed 
  

   immediately 
  before 
  the 
  halogens. 
  By 
  Ramsay 
  at 
  the 
  head 
  of 
  the 
  lithium 
  sodium 
  

   group. 
  

  

  