Bonding

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Chapter 11

• Bonding

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Types of Bonds

• Ionic The electrons of one element are
  transferred to another.
• Covalent Two elements share electrons to obey
  the octet rule.
• Polar covalent The electrons are shared, but
  they spend more time at one element that the
  other.

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Electronegativity

• The energy holding electrons to an atom in a
  chemical bond
• The higher the difference in electronegativity,
  the more polar the bond
• Two identical atoms will have a difference of
  zero and a 100 covalent bond

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Difference in Electronegativity

• Non-polar ?E 0.0 0.4
• Diatomic elements
• C-H (2.5 2.1 0.4)

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Diatomic Elements

• H2, N2, O2, F2, Cl2, Br2, and I2
• Also P4 and S8

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• Polar Covalent ?E 0.5 1.6
• C O (2.5 3.5) ?E 1.0

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• Ionic ?E gt 1.9
• Na Cl (0.9 3.0) ?E 2.1

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Covalent Bonds

• Formation
• Shared electrons
• Orbitals overlap
• Bond length where energy is lowest

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Formation of Covalent Bond
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Normal Covalency
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Covalent Bonds

• Two electrons shared between two elements
• Diatomic elements
• 100 shared
• 100 covalent
• Different elements
• Bond polarity
• Electronegativity

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Multiple Covalent Bonds

• One pair of electrons shared single
• Two pairs of electrons shared double
• Three pairs of electrons shared triple
• All shared electrons are the property of both
  atoms.

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Normal Bonding

• Double Bonds
• CC CO CN PO SO
• Triple Bonds
• CC NN CN

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Formulas, Structures and Shapes

• Formulas
• Molecular Inventory of atoms in molecule
• C2H6O
• Structural Bonding pattern
• CH3CH2OH
• CH3OCH3

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Lewis Structures of Atoms

• We indicate the number of valence electrons using
  a Lewis Structure
• There are four sides around the symbol
• Each side can hold two electrons
• There are a total of eight around the symbol

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Lewis Structures of Molecules

• Find the total number of electrons in the
  molecule.
• Place one pair of electrons for each bond.
• Give surrounding elements eight electrons.
• Place last electrons on central atom.
• If not enough, then form multiple bonds to share
  electrons.

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Examples

• F2

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• O2

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• N2

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• CH4

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• NH3

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• H2O

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• SO3

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• SO2

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• CO2

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VSEPR Theory(Valence shell electron pair
repulsion)

• Two clouds of electons

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• Three pairs of electrons

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0

• Four pairs of electrons

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Lewis Structures of Ions
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• CO32-

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• NH4

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Molecular Polarity
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• BOND polarity based on difference in
  electronegativity
• MOLECULAR polarity based on symmetry of molecule

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