Peiodicity

• How does the ionisation energy change across period 3? and why does this happen?

  • Increases left -> right
  • Nuclear charge increases but shielding remains similar, so there's more attraction between outer e- and nucleus
  • Dips at Al ( change in sub-orbital) and S (e- e- repulsion)
• How does the atomic radius change across period 3? and why does this happen?

  • Decrease left -> right
  • Increased nuclear charge but similar shielding. So there's stronger attraction between outer e- and nucleus
• How does the electroneagtivity change across period 3? and why does this happen?

  • Increases left -> right
  • Increased nuclear charge but similar shielding, so stronger attraction between nucleus and shared pair of electrons
• Define electronegativity

  The ability of an atom of an element to attract a shared pair of electrons across a covalent bond
• Trend in boiling and melting points of Na, Mg and Al

  • Increases left -> right
  • Increase in charge of metal ions and more delocalised electrons.
  • So metallic bonding is stronger
• Why is the boiling point of Si very high?

  • Giant macromolecular structure
  • Large number of covalent bonds
  • Lots of energy needed to break them
• Why does the and BP of Si8 > P4 > Cl2?

  • Bigger molecules
  • Have more van derived waals forces of attraction
  • Need more energy to overcome
• Why is Ar BP and mp very low?

  • Made of small atoms with small van der waals forces between them