﻿ARCHITECTURE 
  OF 
  ATOMS 
  — 
  ABBOT. 
  159 
  

  

  The 
  forces 
  which 
  define 
  atomic 
  positions, 
  orbits, 
  or 
  spheres 
  of 
  in- 
  

   fluence, 
  are 
  electrical 
  attraction 
  and 
  repulsion, 
  and 
  electromagnetic 
  

   effects 
  of 
  electric 
  charges 
  in 
  motion. 
  A 
  neutral 
  atom, 
  which 
  has 
  

   neither 
  furnished 
  free 
  electrons 
  nor 
  captured 
  any, 
  has 
  a 
  definite 
  

   number 
  of 
  orbital 
  electrons, 
  each 
  with 
  its 
  unit 
  electrical 
  negative 
  

   charge, 
  and 
  in 
  the 
  nucleus 
  an 
  excess 
  of 
  protons 
  over 
  bound 
  electrons 
  

   sufficient 
  to 
  make 
  up 
  for 
  the 
  nucleus 
  the 
  same 
  electrical 
  charge 
  as 
  

   carried 
  by 
  orbital 
  electrons, 
  but 
  positive. 
  Although 
  the 
  electrical 
  

   charges 
  of 
  electrons 
  and 
  protons 
  are 
  equal 
  and 
  opposite, 
  the 
  masses 
  

   of 
  the 
  two 
  primitives 
  are 
  greatly 
  unequal. 
  An 
  electron 
  has 
  only 
  

   about 
  one 
  two-thousandth 
  part 
  the 
  mass 
  of 
  a 
  proton. 
  Yet 
  the 
  pro- 
  

   tons 
  are 
  not 
  on 
  that 
  account 
  larger 
  than 
  the 
  electrons 
  in 
  dimensions, 
  

   only 
  exceedingly 
  more 
  massive. 
  

  

  All 
  the 
  usual 
  physical 
  and 
  chemical 
  properties 
  are 
  definitely 
  fixed 
  

   when 
  the 
  excess 
  positive 
  charge 
  of 
  the 
  nucleus 
  is 
  given. 
  The 
  excess 
  

   of 
  positive 
  charge 
  on 
  the 
  nucleus 
  may 
  be 
  gotten 
  in 
  two 
  ways, 
  either 
  

   by 
  adding 
  protons 
  or 
  subtracting 
  electrons 
  from 
  it. 
  To 
  subtract 
  

   electrons 
  scarcely 
  alters 
  appreciably 
  the 
  weight 
  of 
  the 
  atom 
  (atomic 
  

   weight). 
  But 
  to 
  change 
  the 
  number 
  of 
  protons 
  does 
  essentially 
  alter 
  

   the 
  atomic 
  weight. 
  Hence 
  it 
  is 
  that 
  two 
  dissimilar 
  chemicals 
  may 
  

   have 
  about 
  equal 
  atomic 
  weights, 
  for 
  example, 
  bismuth 
  and 
  thorium- 
  

   lead 
  each 
  208; 
  while 
  thorium-lead 
  and 
  uranium-lead, 
  for 
  example, 
  

   which 
  are 
  both 
  quite 
  indistinguishable 
  from 
  each 
  other 
  or 
  from 
  

   ordinary 
  lead 
  (207.20) 
  have 
  atomic 
  weights 
  208 
  and 
  206, 
  respec- 
  

   tively. 
  Readers 
  of 
  the 
  Smithsonian 
  Report 
  for 
  1919 
  will 
  remember 
  

   Doctor 
  Aston's 
  brilliant 
  work 
  along 
  these 
  lines, 
  and 
  further 
  back 
  

   in 
  the 
  report 
  for 
  1918 
  Doctor 
  Richards's 
  telling 
  work 
  on 
  the 
  atomic 
  

   weight 
  of 
  lead. 
  

  

  We 
  are 
  apt 
  to 
  think 
  of 
  solids 
  ordinarily 
  as 
  completely 
  occupying 
  

   the 
  spaces 
  inclosed 
  by 
  their 
  boundaries. 
  Recent 
  knowledge 
  shows 
  

   how 
  radically 
  this 
  notion 
  must 
  be 
  changed. 
  For 
  the 
  protons 
  and 
  

   electrons, 
  which 
  alone 
  can 
  be 
  regarded 
  as 
  really 
  occupying 
  space, 
  

   are 
  certainly 
  more 
  like 
  the 
  motes 
  which 
  dance 
  in 
  the 
  sunbeam 
  in 
  a 
  

   room 
  full 
  of 
  air, 
  than 
  like 
  a 
  structure 
  completely 
  occupying 
  the 
  same 
  

   volume. 
  This 
  shows 
  us 
  how 
  it 
  is 
  possible 
  for 
  metallic 
  wires 
  to 
  con- 
  

   duct 
  electricity. 
  It 
  is 
  the 
  electrons 
  which, 
  flying 
  through 
  the 
  free 
  

   spaces 
  within 
  and 
  between 
  the 
  atoms, 
  are 
  the 
  conducting 
  agents. 
  

   And 
  yet 
  an 
  electron 
  does 
  not 
  have 
  to 
  travel 
  clear 
  along 
  the 
  entire 
  

   length 
  of 
  the 
  wire 
  to 
  give 
  the 
  impression 
  of 
  an 
  electric 
  current. 
  For 
  

   at 
  the 
  positive 
  pole 
  free 
  electrons 
  will 
  be 
  attracted, 
  thus 
  making 
  a 
  

   void 
  of 
  them 
  there, 
  and 
  tending 
  to 
  neutralize 
  the 
  positive 
  pole, 
  while 
  

   at 
  the 
  negative 
  pole 
  they 
  will 
  be 
  repelled, 
  making 
  an 
  excess 
  there 
  

   and 
  tending 
  to 
  neutralize 
  the 
  negative 
  pole. 
  Adjacent 
  regions 
  of 
  

  

  