compounds

• Covalent network compounds


  • silicon oxide
  • silicon carbide
• Ionic compounds


  Have high melting points
• Discrete covalent molecules with pure covalent bonding

  • nitrogen chloride
  • phosphorus hydride
  • carbon sulphide
• In hydrogen fluoride


  Hydrogen has the slight positive charge
• The melting point of silicon oxide will be high because it is a covalent network
• Why ionic compounds do not conduct when solid

  The ions are not free to move
• Bonding in titanium chloride, TiCl4

  Polar covalent
• Lithium fluoride has a higher melting point than lithium bromide


  The ionic bond in lithium fluoride is stronger
• A substance with a melting point of 1053°C that conducts when molten or in solution

  Has ionic bonding
• A substance with a melting point of 1883°C that does not conduct electricity


  Has covalent network bonding
• Sodium iodide


  Is likely to be soluble in water
• Silicon dioxide


  Is likely to be insoluble in water
• Silicon carbide


  • Is hard, because it is a covalent network
• Phosphorus trichloride has a low melting point of -91°C


  Only weak London forces are broken on melting
• Hydrogen chloride vs hydrogen fluoride

  Hydrogen fluoride is more polar