Topic 2 - Bonding , Structure, and the properties of matter

• silicon dioxide (silica)

  • main compound found in sand
  • example of substance with giant covalent structure
  • contains many silicon and oxygen atoms
  • atoms in the structure are linked together by strong covalent bonds
  • atoms in a regular arrangement, forming a giant covalent structure
• High melting and boiling points

  • substances with giant covalent structures are solid at room temperature
  • high melting / boiling point
  • large amount of energy are needed to overcome these strong covalent bonds to make them melt or boil
• conduction of electricity

  • substances with giant covalent structure have no charged particles that are free to move
  • this means it cannot conduct electricity
  • graphite is the only exception
• Diamond's structure and bonding

  • giant covalent structure
  • each carbon atom is joined to four other carbon atoms by strong covalent bonds
  • carbon atoms form a regular tetrahedral network structure
  • no free electrons
• Diamond's properties and uses

  • rigid network of carbon atoms , held together by strong covalent bonds, making it very hard
  • useful for cutting tools e.g. diamond ripped glass cutter
  • high melting point
  • doesn't conduct electricity
• Graphite's structure and bonding

  • giant covalent structure
  • each carbon atom forms three covalent bonds with other carbon atoms
  • carbon atoms form layers of hexagonal rings
  • no covalent bond between layers
  • delocalised electrons from each atom
• Graphite's properties and uses

  • delocalised electron, free to move between layers in graphite
  • this means it can conduct electricity
  • useful for electrodes in batteries and electrolysis
  • forces between layers are weak
  • this means layers can slide over each other
  • also makes graphite slippy
  • useful as a lubricant
• Graphene

  • a single layer of graphite
  • strong covalent bonds between carbon atoms
  • means it has a high melting point and is very strong
  • conducts electricity as it has delocalised electrons
  • useful in electronics and making composites
• Fullerenes

  • molecules of carbon atoms with hollow shapes
  • structures based on hexagonal rings of carbon atoms joined by covalent bonds
  • some fullerenes include rings with five or seven carbon atoms
  • e.g. buckminsterfullerene and nanotubes
• Buckminsterfullerene

  • first fullerene to be discovered
  • molecules made up of 60 carbon atoms joined together by covalent bonds
  • molecules of c60 are spherical
  • weak intermolecular forces between molecules of buckminsterfullerene
  • needs little energy to overcome
  • slippery and has low melting point
• Nanotubes

  • layer of graphene rolled into a cylinder
  • high tensile strength, so strong in tension and resists being stretched
  • strong
  • conducts electricity due to delocalised electrons
  • useful for nanotechnology, electronics and specialised material
• Polymers are long chains of repeating units
• Alloys - a mixture two or more metals

  • new elements of metals distorts the regular arrangement of the other metal atoms
  • this makes it harder for atoms to slide over each other
  • this makes alloys harder than pure metals