Ionic  Bonding,  Ionic  Compounds,  &  Metallic  Bonding    Chemical  Bonds    Chemical  Bond—a  mutual  electrical  attraction  between  the  nuclei  and  valence  electrons  of  different  atoms  that  binds  the  atoms  together.    Chemical  Bonds  create  more  stable  arrangements  of  matter.    3  Types  of  Chemical  Bonds  

1. Ionic  Bonds  2. Covalent  Bonds  

a. Polar  Covalent  Bonds  b. Nonpolar  Covalent  Bonds  

3. Metallic  Bonds    Ionic  Bonding    Cation—a  positive  ion.    An  atom  that  has  lost  electrons.  (metals  form  cations)    Oxidation—loss  of  electrons  (becoming  positively  charged)    Anion—a  negative  ion.    An  atom  that  has  gained  electrons.  (nonmetals  usually  form  anions)    Reduction—process  of  gaining  electrons  (becoming  negatively  charged)    “OILRIG”—Oxidation  Is  Loss,  Reduction  Is  Gain    Ionic  Bonding—chemical  bonding  that  results  from  the  electrical  attraction  between  large  numbers  of  cations  and  anions.  (value  1.7-­‐3.3)  

 

   

Image  Source:  http://galedc.com/uploads/63d92c1b81715e14ccd4012eb1b4aed18504.JPG    Nonpolar  Covalent  Bond—a  covalent  bond  in  which  the  bonding  electrons  are  shared  equally,  resulting  in  a  balanced  distribution  of  electrical  charge  (value  0-­‐0.3).    

Polar  Covalent  Bond—covalent  bond  in  which  the  unbonded  atoms  have  an  unequal  attraction  for  the  shared  electrons  (value  0.3-­‐1.7).    Calculating  Bond  Type—subtract  electronegativities    The  Octet  Rule      Atoms  can  fill  their  outermost  s  and  p  sublevels  by  sharing  electrons  through  covalent  bonding.      Such  bond  formation  follows  the  octet  rule:  Chemical  compounds  tend  to  form  so  that  each  atom,  by  gaining,  losing,  or  sharing  electrons,  has  an  octet  of  electrons  in  its  highest  energy  level.    Exceptions  to  the  Octet  Rule    Exceptions  to  the  octet  rule  include  those  for  atoms  that  cannot  fit  eight  electrons,  and  for  those  that  can  fit  more  than  eight  electrons.    Common  exceptions  to  the  octet  rule:  

Phosphorous  Boron  Hydrogen  

 Electron-­‐Dot  Notation    

 Electron-­‐dot  notation  is  an  electron-­‐configuration  notation  in  which  only  the  valence  electrons  of  an  atom  are  shown,  indicated  by  dots  placed  around  the  element’s  symbol.    

 

 Image  Source:  http://www.middleschoolchemistry.com/img/content/multimedia/chapter_4/lesson_6/lewis_dot_table_big.jpg  

 Ionic  Compounds      

• An  ionic  compound  is  composed  of  positive  and  negative  ions  that  are  combined  so  that  the  numbers  of  positive  and  negative  charges  are  equal.    

 • Most  ionic  compounds  exist  as  crystalline  solids.  

 

• The  strong  attraction  between  ions  in  an  ionic  compound  gives  ionic  compounds  some  characteristic  properties:    

• high  melting  points  • hard  but  brittle    • not  electrical  conductors  in  the  solid  state,  because  the  ions  cannot  move  

 Monatomic  Ions    Many  main-­‐group  elements  can  lose  or  gain  electrons  to  form  ions.    Ions  formed  from  a  single  atom  are  known  as  monatomic  ions.    

Example:  To  gain  a  noble-­‐gas  electron  configuration,  nitrogen  gains  three  electrons  to  form  N3–  ions.    

 Image  Source:  http://preparatorychemistry.com/images/monatomic_ions_PT_CS.jpg  

 Some  main-­‐group  elements  tend  to  form  covalent  bonds  instead  of  forming  ions.    

Examples:  carbon  and  silicon    Naming  Monatomic  Ions    Monatomic  cations  are  identified  simply  by  the  element’s  name.    

Examples:  K+    is  called  the  potassium  cation  Mg2+    is  called  the  magnesium  cation  

 For  monatomic  anions,  the  ending  of  the  element’s  name  is  dropped,  and  the  ending  -­‐ide  is  added  to  the  root  name.    

Examples:  F–    is    called  the  fluoride  anion  N3–  is  called  the  nitride  anion  

 

 Image  Source:  http://www.chem.uwec.edu/Chem103_F08_F0F/pages/resources/media/monoatomic_ions_Silberberg_table_2.3.jpg  

 Binary  Ionic  Compounds    Compounds  composed  of  two  elements  are  known  as  binary  compounds.    In  a  binary  ionic  compound,  the  total  numbers  of  positive  charges  and  negative  charges  must  be  equal.    The  formula  for  a  binary  ionic  compound  can  be  written  given  the  identities  of  the  compound’s  ions.  

 Example:  magnesium  bromide    Ions  combined:  Mg2+,  Br  –    Chemical  formula:  MgBr2  

 

 Image  Source:  http://media.wiley.com/Lux/76/167976.image0.jpg  

 A  general  rule  to  use  when  determining  the  formula  for  a  binary  ionic  compound  is  “crossing  over”  to  balance  charges  between  ions.  

 Example:  aluminum  oxide  

   1)  Write  the  symbols  for  the  ions.     Al3+    O2–  

 2)  Cross  over  the  charges  by  using  the  absolute  value  of  Al2O3  each  ion’s  charge  as  the  subscript  for  the  other  ion.    

 Image  Source:  https://o.quizlet.com/i/2dO466f3ZmRCfpRg6Su2AA_m.jpg  

 

 Image  Source:  

http://faculty.sdmiramar.edu/fgarces/zCourse/All_Year/Ch100_OL/aMy_FileLec/04OL_LecNotes_Ch100/05_CompoundBonding/501_IonicCompounds/501_pic/AlScrisscross.gif  

 

 Image  Source:  https://dr282zn36sxxg.cloudfront.net/datastreams/f-­‐

d%3Abac372a639df48b10edd5d691c3ae4194474123776cbc83c056b1e2c%2BIMAGE%2BIMAGE.1    Naming  Binary  Ionic  Compounds    The  nomenclature,  or  naming  system,  or  binary  ionic  compounds  involves  combining  the  names  of  the  compound’s  positive  and  negative  ions.    The  name  of  the  cation  is  given  first,  followed  by  the  name  of  the  anion:  

 Example:  Al2O3  —  aluminum  oxide  

 Naming  Binary  Ionic  Compounds,  Compounds  Containing  Polyatomic  Ions    Polyatomic  Ion—group  of  atoms  with  a  charge    Many  common  polyatomic  ions  are  oxyanions—polyatomic  ions  that  contain  oxygen.    

 Image  Source:  http://crescentok.com/staff/jaskew/isr/tigerchem/naming/polyions2.gif  

 Writing  Formulas  Containing  Polyatomic  Ions    

   

Image  Source:  https://dr282zn36sxxg.cloudfront.net/datastreams/f-­‐d%3A9bec16749e5a928e14f7889aee7e756e928c7d0a695f930b66675a56%2BIMAGE%2BIMAGE.1  

   The  Stock  System  of  Nomenclature    Some  elements  such  as  iron,  form  two  or  more  cations  with  different  charges.    To  distinguish  the  ions  formed  by  such  elements,  scientists  use  the  Stock  system  of  nomenclature.    The  system  uses  a  Roman  numeral  after  the  cation  to  indicate  an  ion’s  charge.    

Examples:   Fe2+   iron(II)           Fe3+   iron(III)    Metallic  Bonding    Chemical  bonding  is  different  in  metals  than  it  is  in  ionic  or  covalent  compounds.  Metallic  bonding  gives  metals  the  properties  of:  

• Thermal  &  Electrical  Conductivity  • Malleability,  Ductility,  and  Durability  • Luster  • Hardness  &  Strength  

 

 Image  Source:  http://blogs.scientificamerican.com/lab-­‐rat/files/2012/03/metallic-­‐bonding.png  

 The  Metallic-­‐Bond  Model    Valence  electrons  are  free  to  move  about  the  metal.    

• These  mobile  electrons  form  a  sea  of  electrons  around  the  metal  atoms.    

• The  chemical  bonding  that  results  from  the  attraction  between  metal  atoms  and  the  sea  of  electrons  is  called  metallic  bonding.    

• Metallic  bonds  only  exist  between  atoms  of  two  different  metals  or  atoms  of  the  same  metal  element.  

 

 Image  Souce:  http://www.bbc.co.uk/staticarchive/4e6786539008e5012ff9c723c4255ae6fc6c1b9f.gif  

 Alloys—mixture  of  elements  with  metallic  properties.      

 

   

Image  Source:  http://intranet.micds.org/upper/science/chem_02/chem_text_'02/secondsemester/newchaps/solutionscolligativeprops/images/brass.gif