metallic bonding and structure

• Metallic bonding

  • atoms are ionised
  • cations occupy fixed positions in a lattice
  • outer shell electrons are delicalised - shared between all atoms in the metallic structure
• Giant metallic lattice structure

  • the delocalised electrons are spread throughout the structure
  • these electrons can move within the structure
  • it is impossible to tell which electron originated from which particular positive ion
  • over the whole structure, the charges must balance
• giant metallic lattice

  a lattice of positive ions fixed in position and surrounded by a 'sea of electrons'
• High melting points and boiling points

  • the electrons are free to move throughout the structure, but the positive ions remain where they are
  • the attraction between he positive ions and negative delocalised electrons is very strong
  • a high temperature is needed to overcome the metallic bonds and dislodge the ions from their rigid positions in the lattice
• good electrical conductivity

  • the delocalised electron can nove freely, anywhere within the metallic lattice
  • this allows metals to conduct electricity, even in the solid state
• malleability and ductility

  • ductile - can be drawn out or stretched - permits metals to be drawn into wires
  • malleable - can be hammered into different shapes - many metals can be pressed into shapes or hammered into thin sheets
  • delocalised electrons are largely responsible for these properties because they move and so metallic structure has a degree of 'give' which allows atoms or layers to slide past each other
• Period 2 - Li , Be

  Period 3 - Na, Mg, Al

  • structure - giant metallic structure
  • forces - strong forces between the positive ion and delocalised electrons
  • bonding - metallic bonding
• Period 2 - B, C

  Period 3 - Si

  • structure - giant covalent structure
  • forces - strong forces between atoms
  • bonding - covalent bonding
• Period 2 - N2, O2, F2, Ne

  Period 3 - P4, S8, Cl2, Ar

  • structure - simple molecular structure
  • forces - weak intermolecular forces
  • bonding - covalent bonding between molecules , intermolecular bonding between molecules