periodicity

• s, p, d blocks


  Classification of elements according to which orbitals the highest energy electrons are in
• Elements


  • Classified as s, p or d block
  • Highest energy electrons are in different orbitals
• Atomic radius decreases from left to right across a period
• Exactly the same trend in period 2
• Periodicity


  Repeating pattern across different periods
• Properties that display periodicity

  • Atomic radius
  • Melting points
  • Boiling points
  • Ionisation energy
• Elements are arranged in increasing atomic number in the periodic table

  
• Elements in Groups have similar physical and chemical properties
• Periods


  • Period 2 = Li, Be, B, C, N, O, F, Ne
  • Period 3 = Na, Mg, Al, Si, S, Cl, Ar
• First ionisation energy


  Energy needed to remove an electron from each atom in one mole of gaseous atoms
• The equation for 1st ionisation energy always follows the same pattern
• Factors affecting ionisation energy

  • Attraction of the nucleus
  • Distance of electrons from nucleus
  • Shielding of nuclear attraction
• Successive ionisation energies for an element give information about electronic structure
• Big jump between 4th and 5th ionisation energies

  Indicates the 5th electron is in an inner shell closer to the nucleus with less shielding
• Helium has the largest first ionisation energy
• Metallic bonding


  Electrostatic force of attraction between the positive metal ions and the delocalised electrons
• Factors affecting strength of metallic bonding

  • Number of protons/Strength of nuclear attraction
  • Number of delocalised electrons per atom
  • Size of ion
• Types of bonding and examples

  • Covalent: Diamond, Graphite, Silicon dioxide, Silicon
  • Metallic: Magnesium, Sodium
  • Macromolecular: Diamond, Graphite
• Macromolecular structures


  • Giant molecular structures with very high melting points due to strong covalent bonds
• Giant metallic lattice


  • Shiny metal, malleable as planes of identical positive ions can slide over each other
• Melting and boiling points

  Metallic bonding: high due to strong bonding

  Macromolecular: very high due to many strong covalent bonds

  Simple molecular: low due to weak intermolecular forces
• Similar trend in melting and boiling points in period 2