Chemical Bonding - Get as PowerPoint by Dofz1YtU

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									Chemical Bonding


  Ionic and Covalent
Chemical Bond
 Forms between atoms if their valence
  electrons make a new arrangement
  that has less energy then their
  previous arrangement (more stable
  together than separate)
 Atoms can lose, gain or share
  electrons to form bonds
Review: Octet Rule:
 When atoms combine, bonds form so
  that each atom finishes with an octet
  (8) valence electrons
Review: Ionic Bonds:
 Between cations (+) and anions (-)
 Is an attraction between oppositely
  charged ions
 Metal ion “gives” electrons to non-
  metal ion
 Ex : NaCl
         Na “gives” one e- to Cl
Covalent Bonds
 Between 2 non-metal ions
 Share one or more pairs of electrons
 **A neutral particle that is composed
  of atoms joined by covalent bonds is
  called a Molecule.
 Substances that are composed of
  molecules are called Molecular
  Compounds.
Covalent bonding
 A single bond is formed when one
  pair of electrons is shared.
 In a double bond 2 pairs and in a
  triple bond 3 pairs of electrons are
  shared
 Example: diatomic molecules, like
  O2, H2, N2, F2, Cl2…
Diatomic molecules
• A diatomic molecule is a molecule
  made of two of the same atoms.
• Hydrogen exists as a diatomic
  molecule.
• It bonds with itself to form the
  molecule H2.
     Electron dot diagram:

              H· + ·H H:H
Other diatomic molecules:
• A total of seven elements exist as
  diatomic molecules rather than as
  individual atoms.
• They are; H2, N2, O2, F2, Cl2, Br2, I2
• Remember; “HOBrFINCl”….hehe
Single bonds
Lewis structures
 also called Lewis-dot diagrams
 are diagrams that show the bonding
  between atoms of a molecule and
  other electrons that may exist in the
  molecule.
Representing Covalent Molecules:
 No Arrows!
 Use circles to show shared pairs of
  electrons
 Draw electron dot diagrams side by
  side and see if pairs of electrons can
  be shared.
 Remember one electron in pair must
  come from each atom.
Examples:
   Br2        CBr2F2
   O2         H2O
   N2         CO2
   CH4        H2 S
   SiH4       GeH4
   CBr4       C 2 H2

								
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