Chemical Bonding: The Covalent Bond Model

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Chemical Bonding The Covalent Bond Model
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Chemical Bonds

• Forces that hold atoms to each other within a
  molecule or compound

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Ionic Bonds

• Attractive force holding oppositely charged ions
  together
• Ions can be monoatomic or polyatomic
• Involve charged metal ion (or NH4) and
  charged non-metal ion
• Results in formation of an ionic compound

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Covalent Bonds

• Attractive force between a non-metal and a
  non-metal
• Involves sharing of electrons
• Results in formation of a covalent compound (a
  true molecule)

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Covalent bonding can occur due to orbital overlap
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Lewis structures can help determine how many
covalent bonds will form
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What are these?

• Bonding electrons
• Non-bonding electrons
• Single bond
• Double bond
• Triple bond
• Coordinate covalent bond

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Drawing Lewis Structures of Molecules

• Count the total number of valence electrons
  available (add or subtract for polyatomic ions)
• Place chemical symbols in tentative arrangement
• Make single bonds
• Fill outer atoms with non-bonding pairs
• Place remaining electrons on central atom(s)
• Check the structure and make double or triple
  bonds if needed

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Electronegativity

• How strongly an atom pulls electrons towards
  itself

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Using electronegativity to predict bond type

• Non-polar covalent (electroneg dif lt0.5)
• Polar covalent (electroneg dif 0.5 - 1.5)
• Ionic (electroneg dif gt1.5)

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VSEPR Method for predicting molecular geometry
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Bond polarity and molecule geometry are used
together to predict molecule polarity
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