3.1.1 Periodicity

• Periodicity is a repeating pattern of properties across different periods
• Atomic radius decreases as you move left to right. This is because the number of protons increase, creating a positive charge for electrons in the same shell
• First ionisation energy is the energy needed to remove an electron from one mole of gaseous atoms
• Factors affecting ionisation energy:

  1. Attraction of nucleus (more protons = greater attraction)
  2. Distance of electrons from nucleus (bigger atom = outer electrons further away = weak nuclear attraction)
  3. Shielding of attraction of nucleus
• Metallic bonding is electrostatic attraction between positive metal ions and delocalised electrons.
• Factors affecting metallic bonding:

  1. Strength of nuclear attraction (more protons = stronger bond)
  2. Number of delocalised electrons per atom (outer shell electrons are delocalised)
  3. Size of ion (smaller ion = stronger bond)
• Bonding - Covalent

  Structure - Macromolecular (giant molecular).

  Examples - Diamond, graphite, silicon dioxide, silicon.
• Bonding - Metallic

  Structure - Giant metallic lattice

  Examples - All metals.
• Macromolecular:

  • Melting and boiling points - High because of many strong covalent bonds in structure. Takes a lot of energy to break.
  • Solubility in water - Insoluble.
  • Conductivity when solid - Diamond and sand is poor because electrons can't move (localised). Graphite is good because free delocalised electrons between layers.
  • Conductivity when molten - Poor.
  • General description - Solid.
• Giant metallic:

  • Melting and boiling points - High because of strong electrostatic forces between positive ions and sea of delocalised electrons.
  • Solubility in water - Insoluble.
  • Conductivity when solid - Good because delocalised electrons can move through structure.
  • Conductivity when molten - Good.
  • General description - Shiny metal. Malleable as positive ions in the lattice are identical, so planes can slide easily over one another (attractive forces in lattice is same whichever ions are adjacent).