Periodic trends in bonding and structure

• The elements near the non-metal/metal divide can show in-between properties (some metal, some non-metal properties) and are called semi-metals or metalloids.
• Metallic bonding is the strong electrostatic attraction between delocalised electrons and the fixed cations.
• Metals do not dissolve. It might be expected that there would be some interaction between polar solvents and the charges in a metallic lattice, as with ionic compounds, but any interactions would lead to a reaction, rather than dissolving.
• Across period 2 and period 3,

  • the melting point increases from group 1 to group 4
  • there is a sharp decrease in melting points between group 4 and group 5
  • the melting points are comparatively low from group 5 to group 0
• The sharp decrease in melting point between group 4 and group 5 marks a change from giant to simple molecular structures. On melting, giant structures have strong forces to overcome so have high melting points. Simple molecular structures have weak forces to overcome, so have much lower melting points