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Lewis Dot Structures and Bonding

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Lewis Dot Structures and Bonding Powered By Docstoc
					Making
Bonding
Models
          Today We Will…

 Describe  the two main ways
  elements bond
 Construct Lewis Dot Diagrams
 Identify characteristics of Ionic and
  Compounds
 Define cation and anion
            Bonding
   Bonding is the sharing or transferring
    of electrons between elements in
    order to combine to form molecules or
    compounds.
      Types of Bonds
Metal + Nonmetal = Ionic
 (transfer)
Nonmetal + Nonmetal = Covalent
 (share)
Metal + Metal = Metallic (sea of
 electrons)
   Bonding possibilities
(1) They can try to gain electrons to fill
  up their last shell. (IONIC)
                     OR
(2) They give up electrons and have a
  filled lower shell. (IONIC)
                     OR
(3) They share a few electrons and have
  a filled shell. (COVALENT)
         Lewis Dot Diagrams
 Discovered by Lewis
 It is a diagram for each element that depicts that
  element’s valence electrons
 Valence Electrons: electrons on the outer shell of
  an element.
 This will help
us tell how
elements will
bond!!!
             Learning Check
      
A.   X would be the electron dot formula for
     1) Na                 2) K           3) Al
       
B.    X    would be the electron dot formula
       

     1) B           2) N           3) P
How do we know the valence electrons of an
               element?
   GROUPS!!
   Label the valence electrons according to their groups.
                  Ionic Bond
Definition:-bond formed between two ions
    by the transferring of electrons
 Ionic bonds only form between a metal
    and a nonmetal with different
    electronegativities.
 Electronegativity- tendency of an atom
    to attract electrons
     The more electrons the atom has the more
      elctronegative it is.
Which has the highest
  electronegativity
      Ionic Bonds form Ions
•   Metals become cations (+ charged)



•   Nonmetals become anions (-
    charged)
Octet Rule = atoms tend to gain, lose or share
electrons so as to have 8 electrons
      C would like to Gain 4 electrons
      N would like to Gain 3 electrons
      O would like to Gain 2 electrons
Helium, neon and argon are atoms which do not
react with other atoms.

Each of these gases has a full outer electron shell
(orbit).


   2p2n             10p10n                18p22n




 He
      4
      2
                    Ne20
                      10
                                             40
                                          Ar 18
                     2,8
                                           2,8,8
                                     Chemical Bonds.mht


                           Na
The Sodium atom has        e.c. 2,8,1
1 Electron in it’s outer   Atom

shell.



The Sodium loses 1         (Na +)                                 +
                           e.c. (2,8)+
electron to leave a        Ion
complete outer shell.
It is now a Sodium ion           All Things Science - Ionic and
with a charge of 1 +             covalent bonding animation.mht
The Chlorine atom             Cl

has 7 electrons in it’s       e.c. 2,8,7
                              Atom
outer shell.


                                           -
                              (Cl - )
The Chlorine gains 1 electron
                          e.c. (2,8,8)-
to gain a complete outer Ion
shell.
It is now a Chlorine ion with
a charge of 1 -
                 Oxidation Numbers
   The plus or minus indicates if electrons were lost or
    gained.
   The number indicates how many electrons.
              Ionic Bond

1. Write the symbol for each element
2. Draw the Electron Dot Diagram
3. Draw an arrow to show the transfer
   of electrons
4. Make sure the sum of the ions equals
   zero
              Ionic Bond

1. Write the symbol for each element
2. Draw the Electron Dot Diagram
3. Draw an arrow to show the transfer
   of electrons
4. Make sure the sum of the ions equals
   zero
              Ionic Bond

   Magnesium (Mg) + Fluorine (F)




Don’t forget to show the oxidation number
         and the chemical formula.
           Ionic Compounds


•Held together by strong electrostatic
forces
• High melting points and boiling points
• When melted or dissolved ionic
compounds conduct electricity
Covalent Bonding
             Today We Will
 Describe  and draw covalent bonding
 Identify characteristics of covalent
  compounds
 Define diatomic atom
             Lets Review
 How  many valence electrons makes an
  atom stable? What is this called?
 Draw the Lewis Dot Diagram for Sulfur
 An ionic bond is between a _______ and a
  ______.
 An ionic bond forms when electrons are
  _______ or _______.
            Covalent Bond

 Atoms still want to achieve a noble
  gas configuration.
 Bond formed by sharing electrons
 Occurs between non metals
 Results in the formation of a
  molecule
              Covalent Bond

1.   Write the symbol for each element
2.   Draw the Electron Dot Diagram
3.   Rearrange the electrons to pair up
     with electrons from each atom
4.   Draw circles to show sharing of
     electrons
5.   Draw the bond structure for each
     pair of electrons shared.
            Covalent Bond

   Hydrogen (H) + Hydrogen (H)


         H°       °H
Each hydrogen atom wants to gain
one electron to achieve an octet
The octet is achieved by each atom
sharing the electrons in the middle.
            Covalent Bond

   Hydrogen (H) + Hydrogen (H)


         H°       °H

The pair shared in the middle is called a
bonding pair. Since there is only one
bonding pair we call this a single bond.
           Covalent Bond

   Hydrogen (H) + Hydrogen (H)


          H         H

Single bonds are represented with a dash.
    O                O
Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.
      O O
Both electron pairs are shared.
O O
   6 valence electrons
 plus 2 shared electrons
       = full octet
    O O
 two bonding pairs,
making a double bond
             Diatomic Atoms
 Elements that are naturally in molecules
 with 2 atoms each

H   O N Cl Br I F
       Covalent Compounds
 Forces between molecules are weak.
 Usually gas or liquids
 Low melting point and boiling point
 No overall electrical charge
          Classwork/Homework

1. H2S             1. NH3
2. F2              2. PBr3
3. HF              3. CCl4
4. H2O             4. CS2
5. AlF3            5. CO2
6. MgO             6. K2S
                   7. CH4

				
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posted:8/8/2012
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