Formation of Ions & Ionic Compounds: Electron Configurations, Bonding, & Properties, Exams of French

Download Formation of Ions & Ionic Compounds: Electron Configurations, Bonding, & Properties and more Exams French in PDF only on Docsity! Forma&on  of  Ions   Forma&on  of  Ions   •  Elements  tend  to  lose  or  gain   electrons  to  fill  their  outermost   energy  levels  with  eight  electrons   depending  on  their  electron  affinity   •  As  a  general  rule,  metals  will  give   electrons  away  and  nonmetals  will   accept  electrons.   Forma&on  of  Ions   •  The  charge  of  an  ion  can  be   computed  by  subtrac&ng  the   number  of  protons  by  the  new   number  of  electrons:   n  Chlorine  would  gain  1  electrons  so:        17  -­‐  18  =  -­‐1  charge   Forma&on  of  Ions   n  Sodium  would  lose  1  electrons  so:          11  -­‐  10  =  +1   •  An  ion  and  its  charge  is  represented   by  the  element's  symbol  and  then   the  charge  is  wriAen  aZer  it  as  a   superscript:   Na+1 Cl-1 Forma&on  of  Ions   •  The  general  term  for  a  posi&ve  ion   is  a  ca#on.   •  The  general  term  for  a  nega&ve   ion  is  an  anion.   Forma&on  of  Ions   •  Unfortunately,  since  the  transi&on   metals  have  only  two  electrons  in   their  outermost  energy  level,  we   cannot  use  the  Rule  of  Eight  to   determine  their  ionic  charge.   Forma&on  of  Ions   •  To  accommodate  this,  we  will   assume  that  an  ion  of  a  transi&on   metal  will  be  +2  unless  otherwise   stated  (they  have  the  ability  to  have   more  than  one  oxida&on  number).   Ionic  Compounds   Structure  of  ionic  compounds   •  The physical properties of ionic compounds are very different from metals. •  The structure of ionic compounds must therefore be very different from those present in metals. •  What do we already know about ionic compounds. What do the properties tell us? Tas.e 6.1 The physical properties and inferred structural features of sodium chloride Property of NaCl What this tells us about structure High melting temperature Forces between the particles are strong Hard, brittle crystals Forces between the particles are strong Does not conduct electricity in the solid — No free-moving charged particles present in state solid sodium chloride Conducts electricity in the molten state Free-moving charged particles present in molten sodium chloride Structure   •  From the properties we can conclude: – The forces between the particles are strong. – There are no free-moving electrons present, unlike in metals. – There are charged particles present, but in solid state they are not free to move. – When an ionic compound melts, however, the particles are free to move and the compound will conduct electricity. Using  the  ionic  bonding  model  to  explain   the  proper&es  of  sodium  chloride   High  Mel&ng  Temperature   •  Ever  no&ced  that  when  you  eat  french  fries  the  food   may  be  hot  but  the  salt  does  not  melt.   •  This  is  because  to  melt  and  ionic  solid  energy  must   be  provided  to  allow  the  ions  to  break  free  and   move.   •  NaCl  has  a  high  mel&ng  temp,  this  indicates  a  large   amount  of  energy  is  needed  to  reduce  the   electrosta&c  aArac&on  between  the  oppositely   charged  ions  and  allow  them  to  move  freely.   Hardness  and  BriAleness   •  Unlike metals ionic compounds are not malleable. They break when beaten. •  A force can disrupt the strong electrostatic forces holding the lattice in place. •  A sodium chloride crystal cannot be scratched easily but if a strong force (a hammer blow) is applied it will shatter. •  This is because the layers of ions will move relative to each other due to the force. •  During this movement, ions of like charge will become adjacent to each other. Resulting in repulsion Reac&ons  of  metals  with  non-­‐metals   •  Metallic atoms have low ionization energies and low electronegativities. •  Non-metallic atoms have high ionization energies and low electronegativities. •  In other words metallic atoms lose electrons easily and non-metallic atoms gain electrons easily. Ionic  Compounds   •  So the metal atoms lose an electron to the non-metal atoms. •  In doing so, both atoms will often achieve the electronic configuration of the nearest noblest gas, which is particularly stable. Sodium  Chloride   •  When sodium reacts with chlorine: •  Na atom (1s2 2s2 2p6 3s1) loses an electron to become 1s2 2s2 2p6 (the same as Neon) •  Cl atom (1s2 2s2 2p6 3s1 3p5) gains an electron to become 1s2 2s2 2p6 3s1 3p6 (the same as argon) Chemical  Formulas   •  Almost every compound in which a metal is combined with a non-metal displays ionic bonding. •  The formulas of simple ionic compounds, such as NaCl and MgCl2 can be predicted from the electron configurations of the atoms. Wri&ng  Formulas:  Rules   •  Chemical formulas are part of the language of chemists. To understand and use this language, you need to follow a number of fules. Wri&ng  Formulas:  Rules   Simple  Ions   •  The  posi&ve  ion  is  place  first  in  the  formula,  the   nega&ve  ion  is  second.     •  For  example:    KF,  CuO   •  Posi&ve  and  nega&ve  ions  are  combined  so  that  the   total  number  of  posi&ve  charges  is  balanced  by  the   total  number  of  nega&ve  charges.     •  For  example,  CuS,  CuCl2,  AlCl3  and  Al2O3   •  When  there  are  two  or  more  of  a  par&cular  ion  in  a   compound,  then  in  the  chemical  formula  the  number   is  wriAen  as  a  subscript  aZer  the  chemical  symbol.    For  example,  Al2O3   Metallic  Bonds   Cations packed in ‘a sea of electrons” oO © Ot O-¢ 00:00 9900 0.000 o000 Metals   •  Metals consist of closely packed cations floating in a “sea of electrons”. •  Delocalized electrons •  All of the atoms are able to share the electrons. •  The electrons are not bound to individual atoms. Body  Centered  Cubic   Chromium : ea Face-Centered Cubic ext Hexagonal Close-Packed z An http://phycomp.technion.ac.il/~pavelba/hcpS. gif Zinc Alloys   •  Stainless Steel – Fe 80.6%, Cr 18%, C 0.4%, Ni 1% •  Cast Iron -Fe 96%, C 4% Types  of  Alloys   •  Two types of formation: – Substitutional alloys • Similar size atoms – replacement – Interstitial alloys • Different size atoms – smaller ions fill interstices (spaces between atoms)