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									Covalent Bonding




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Ratio of Atoms in Covalently Bonded
Molecules

   In Ionic compounds the molecular formula
    represents the repeating pattern (ratio of
    atoms).
   In Covalent Compounds the molecular
    formula give information regarding one full
    unit.
Ionic Example: NaCl


   We do not have one molecule containing one
    sodium atom and one chlorine atom.
   NaCl represents ratio of Na to Cl.
   NaCl will always give the same structure
Covalent Bonding Example

   Acetone – C3H6O
   Allyl Alcohol - C3H6O
Demo

   The power of acetone
D-Glucose
Drawing Lewis Structures for
Covalently Bonded Compounds

   Draw Lewis Symbols as in Ionic Compounds
   Instead of stealing elections the atoms share
   Shared electrons are represented by a dash
HF

   The stable octet is achieved by sharing
    electrons.
Octet Rule




   In Ionic bonding electrons are gained or lost.
   In Covalent bonding electrons are shared.
Fluorine Gas
   Why am I not drawing any symbols with
    square brackets as I did on Monday?
Example with more than one bond
Predicting # of Bonds

   The number of bonds can be predicted by
    counting the number of single valence electrons.

    Atom            Valence e-      Single e-
    Carbon                 4               4
    Nitrogen               5               3
    Oxygen                 6               2
    Chlorine               7               1
Single, Double or Triple

   Covalent bonds and contain one pair, two
    pairs or three pairs of bonding electrons.
   One pair = single bond (Sigma bond) σ
   Two pairs = double bond (second Pi bond) π
   Three pairs = triple bond (third Pi bond) π
Structural Formula

   Similar to the Lewis Structure but without the
    electrons. Just show atomic symbols and the
    covalent bonds.
   Work on Question #1 page 77.
   We will go over together in 10 min.

   Correction (error in book)
   Draw a Lewis structure and write the
    structural formula for each of the following:
Coordinate Covalent Bonding

   Is a covalent bond, where both the shared
    electrons come from one atom.
Covalent vs Ionic

   Covalent Bonds are stronger
   Covalent Molecules weakly interact with
    other covalent molecules so the melt/boil at
    lower temperatures.
   Ionic Compounds form conductive solutions
    whereas molecular one tend to not form
    conductive solutions.
Intermolecular vs Intramolecular

   What does Intermolecular forces mean?
    –   Attractive forces between different molecules or
        ions.
   What are Intramolecular forces?
    –   Attractive forces between atoms within the same
        compounds.
   Please pages 79 and 80 in aid in completing
    your homework.
Homework

   p79 #2
   p80 #3,4
   p81 #6,10,11,13,14

   Hints: Question #10 read p 79
   Please read over all questions before you
    leave so you can get help on difficult
    questions.

								
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