Covalent bonding

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Covalent bonding

• AH Chemistry Unit 1(b)

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Potential energy diagram
Bond dissociation energy
Bond length (distance between nuclei at minimum
energy)
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Lewis formulae
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Dative covalent bonds

• Co-ordinate covalent bonds

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Writing Lewis formulae

• Calculate total valence electrons
  for ions, add or subtract electrons
  accordingly
• Write skeleton structure
  more electronegative atoms usually surround
  central atom
• Distribute electrons to atoms surrounding central
  atom
• Distribute remaining electrons to central atom

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Examples

• SCl2
• COCl2
• BF4-

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Resonance structures

• Represents delocalised bonding
• You describe the electron structure of a molecule
  having delocalised bonding by writing all
  possible electron-dot formulae

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Ozone
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Sulphur dioxide
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Carbonate ion
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Exceptions to the octet rule

• BCl3
• PCl5