structure and bonding

• Ionic bonding


  Bonding between a metal and a non-metal where one or more electrons are transferred
• Ionic compounds form giant ionic lattices
• Each ion in an ionic compound is surrounded by ions of the opposite charge
• Covalent compounds

  • H
  • H2O
• Charge


  The overall charge of an ionic compound is zero
• Ionic compounds have high melting and boiling points due to the strong forces of attraction between the oppositely charged ions
• Ionic compounds can conduct electricity when molten or in aqueous solution
• Small covalent molecules


  • Usually gases or liquids at room temperature
  • Held together by strong covalent bonds, with weak intermolecular forces
  • Require much less energy to break apart than ionic compounds
• As the size of covalent molecules increases, the intermolecular forces increase as well</b>
• Covalent compounds do not have an overall electrical charge
• Giant covalent molecules


  Contain millions of covalent bonds
• Giant covalent substances are always solids at room temperature
• Giant covalent substances have high melting and boiling points
• Diamond


  • Formed from the element carbon
  • Each carbon atom forms covalent bonds to four other carbon atoms
• Representing diamond


  1. Carbon atoms shown as circles

  2. Covalent bonds shown as sticks
• Even a tiny diamond contains millions and millions of carbon atoms joined by covalent bonds
• Melting diamond


  Requires breaking all the covalent bonds, which takes a huge amount of energy
• Diamond cannot conduct electricity
• Silicon dioxide (silica)


  • Contains the elements silicon and oxygen covalently bonded together
• Silicon dioxide has a very high melting and boiling point
• To melt silicon dioxide, the covalent bonds must be broken, which takes a great deal of energy
• Graphite


  Another form of carbon, a giant covalent molecule
• Graphite


  • Soft and slippery
  • High melting and boiling point
  • Good conductor of electricity and heat
• Structure of graphite


  1. Carbon atoms form covalent bonds to 3 other carbon atoms

  2. Carbon atoms form hexagonal rings

  3. Hexagonal rings arranged into layers

  4. No covalent bonds between layers
• No covalent bonds between layers in graphite


  Layers can slide over each other, making graphite soft and slippery
• Graphite contains many strong covalent bonds


  Requires a lot of energy to melt graphite, explaining its high melting and boiling point
• Delocalized electrons in graphite

  Electrons in the outer energy level of carbon atoms that are not in covalent bonds, can move and conduct electricity and heat
• Graphite has delocalized electrons


  Similar to metals, which also have delocalized electrons that can move and conduct electricity and heat
• Graphite is not a metal, it is formed from the element carbon
• Graphene


  A single layer of graphite
• Graphene


  • Good conductor of electricity
  • Extremely strong
  • High melting and boiling point
• Fullerenes


  Molecules based on carbon atoms with hollow shapes, usually hexagonal rings but can also have 5 or 7 carbon atoms
• Fullerene


  • Buckminsterfullerene (C60)
• Fullerenes


  • Can be used to deliver drugs
  • Can be used as lubricants
  • Can be used as catalysts
• Carbon nanotubes


  Fullerenes shaped into long cylinders with a relatively small diameter
• Carbon nanotubes


  • High tensile strength
  • Good conductors of electricity
  • Good conductors of heat
• Polymer


  Very large molecule made by joining together thousands of small identical molecules called monomers
• Monomer


  Small identical molecule that polymers are made from, often alkene molecules
• Monomer


  • Ethene
• Forming a polymer


  Join together thousands of monomer molecules