structure and bonding

• ionic bonding

  • elements react in order to achieve a full outer shell, achieve the full outer shell of a noble gas
• ion is an atom with an overall charge
• • group 1 metals lose one electron forming a positive ions
  • group 7 ions gain one electron forming a negative ion
• • group 2 metals lose 2 electrons forming a 2+ ion
  • group 6 metals gain 2 electrons forming a 2- ion
• giant ionic lattice

  • positive ions are surrounded by negative ions
  • very strong forces of attraction (electrostatic forces of attraction) hold the positive and negative ions in place (ionic bonds act on all directions)
  • 3d shaped
• ionic compounds

  • very high melting and boiling point
  • the electrostatic forces of attraction require a lot of heat energy to break
  • cannot conduct electricity when solid, ions can vibrate but not move
  • can conduct electricity when dissolved in water or melted, ions can move
• covalent bonding is when non metals bond together
• ionic bonding when metal and non metal bond together
• covalent bonds

  • strong bonds
  • shown in energy level diagrams or dot and cross diagrams or stick diagrams
  • sharing bonds
• properties of small covalent molecules

  • low melting and boiling points = increasing temperature in a liquid causes the intermolecular bonds to break
  • very weak intermolecular forces between atoms with strong covalent bonds
  • don't conduct electricity = do not have an overall electric charge
• giant covalent substances

  • diamond
  • silica
  • graphite
  • always solids at room temperature = high melting and boiling points
  • require lots of energy for millions of covalent bonds to break
• diamond

  • formed from carbon
  • very high melting and boiling point
  • cannot conduct electricity = outer electrons are in covalent bonds so no free electrons to carry electron charge
• silicon dioxide

  • contains silicon and oxygen covalently bonded together
  • very high melting and boiling point = strong covalent bonds
• graphite

  • formed from carbon (6 atoms hexagonal)
  • soft and slippery = layers slide over each other
  • very high melting and boiling point = lot of energy
  • good conductor of heat and electricity = delocalised electrons can move between the layers
  • graphite has similar Properties but NOT METAL
• graphene

  • single layer of graphite (one atom thick)
  • good conductor of electricity = delocalised electrons which move through the graphene molecule carrying electrical charge
  • extremely strong and high melting / boiling point = strong covalent bonds
• fullerene

  • hollow shapes (carbon atoms)
  • buckminsterfullerene is the first fullerene molecule to be discovered (60 carbon atoms)
  • used to deliver drugs
  • lubricants = reduce friction between moving parts
  • used as catalyst to speed up chemical reactions
  • carbon nanotubes = fullerenes shaped into a long cylinder with a small diameter: high tensile strength, delocalised electrons - good conductors of heat and electricity, reinforce material
• bonding in polymers

  • very large molecules made by joining thousands of monomer molecules (alkene molecules)
• metallic bonding when two metals bond together
• properties of metals

  • strong metallic bonds
  • high melting and boiling points
  • conduct electricity = delocalised electrons carrying an electric charge or thermal energy move
  • can be bent or shaped = layers of atoms can slide over each other
• alloys

  • copper, gold, iron, aluminium
  • harder than pure metals
  • mixture of metals
  • different sizes of atoms distorts the layers making it more difficult for metals to slide over each other