bonding and compounds

• ionic bonding is the transfer of electrons
• ionic bond


  when a metal and non-metal react the metal loses electrons to form positively charged ions and the non-metals gain these electrons to form a negatively charged ion.

  these oppositely charged ions are strongly attracted to one another by electrostatic forces
• dot and cross diagrams are used to show how ionic compounds are formed
• ionic compounds have a structure called giant ionic lattice
• ionic compound properties

  • high melting point
  • high boiling point
  • when solid, ions are holding place so compounds can't conduct electricity
  • when compounds melt ions are free to move and can carry electric charge
• covalent bonds


  when non-metal atoms bond together they share pairs of electrons
• covalent bonds are bonded by electrostatic forces, making them very strong
• simple molecular structure examples:

  • hydrogen H2
  • oxygen O2
  • methane CH4
  • chlorine Cl2
  • nitrogen N2
  • water H2O
  • hydrogen chloride HCl
• simple molecular strictures are weak
• polymers


  long chains of repeating units
• all the atoms in a polymer are bonded by covalent bonding
• giant covalent structures ar macromolecules
• giant covalent structures examples:

  • diamond
  • graphite
  • silicon dioxide
• diamond structure


  every carbon atom forms four covalent bonds - very strong
• graphite


  contain sheets of hexagons

  each carbon atom forms three covalent ones
• there aren't any covenant bonds between the layers of graphite - they are held together by weak intermolecular forces, so they are free to move over each other

  this makes graphite soft and slippery so it is an ideal lubricating material
• why can graphite rub off the pencil to paper?

  the layers of graphene are held together by weak intermolecular forces which means that they can easily slip over each other and get onto the paper
• only three out of each carbons four outer electrons are used in bonds

  so each carbon has one delocalized electron that can move

  so graphite conducts electricity.
• fullerenes are molecules of carbon, shaped like closed tubes or hollow balls
• fullerenes


  can be used to cage other molecules

  this could be used to deliver a drug into the body
• nanotubes


  tiny carbon cylinders
• nanotubes have very high tensile strength (they don’t break when stretched) and electrical conductivity
• diamonds are hard because there are no gaps between the carbon atoms and all the bonds are strong
• metallic bonding involves delocalised electrons
• metallic bonding


  electrostatic attraction between positive metal ions and the shared negative electrons - very strong
• metal properties

  • usually solid at room temperature
  • good conductors of electricity and heat
  • most metals are malleable
• alloys


  a mixture of two or more metals or a metal and another element

  they are harder and more useful than pure metals