Crystals

• Ionic crystals - melting and boiling points

  High melting and boiling points

  Lots of strong ionic bonds between the positive and negative ions so lots of energy is needed to overcome the strong electrostatic attraction
• Ionic crystals - electrical conductivity

  Can’t conduct electricity when solid

  No ions free to move to carry the charge throughout the structure

  
  

  Can conduct electricity when liquid or aqueous

  Ions are free to move to carry the charge throughout the structure
• Ionic crystals - strength

  Very strong

  Lots of strong ionic bonds between the positive and negative ions
• Metallic crystals - melting and boiling points

  High melting and boiling points

  Lots of strong metallic bonds between positive ions and delocalised electrons so lots of energy needed to overcome the strong electrostatic attraction

  Increases with ion charge - stronger electrostatic attraction and more delocalised electrons
• Metallic crystals - electrical conductivity

  Can conduct electricity

  Delocalised electrons are free to move to carry the charge throughout the structure
• Metallic crystals - strength

  Strong

  Lots of strong metallic bonds between the positive ions and delocalised electrons

  Increases with ion charge - stronger electrostatic attraction and more delocalised electrons

  Increases with smaller ions - electrons are closer to the positive nucleus so stronger electrostatic attraction
• Metallic crystals - malleability

  Malleable

  Ions can move when hit so the layers of metal atoms can slide relative to each other
• Diamond - melting and boiling points

  High melting and boiling points

  Each carbon atom has 4 covalent bonds

  Lots of strong covalent bonds that need lots of energy to overcome
• Diamond - electrical conductivity

  Can’t conduct electricity

  No delocalised electrons free to move to carry the charge throughout the structure
• Diamond - strength

  Strong

  Lots of strong covalent bonds
• Graphite - melting and boiling points

  Very high melting and boiling points

  Lots of strong covalent bonds so lots of energy is needed to overcome
• Graphite - electrical conductivity


  Can conduct electricity

  Each carbon atom has 3 covalent bonds

  Each carbon atom has a delocalised electrons that is free to move to carry the charge throughout the structure
• Graphite - strength

  Strong

  Lots of strong covalent bonds

  Soft

  Layers can slide relative to each other
• Graphene - melting and boiling points

  Very high melting and boiling points

  Lots of strong covalent bonds so lots of energy is needed to overcome
• Graphene - electrical conductivity

  Can conduct electricity

  Each carbon atom has 3 covalent bonds

  Each carbon atom has a delocalised electron that is free to move to carry the charge throughout the structure
• Graphene - strength

  Strong

  Lots of strong covalent bonds

  Soft

  Layers can slide relative to each other
• Simple molecular crystals - melting and boiling points

  Low melting and boiling points

  Has covalent bonds but breaking VDW forces

  VDW forces between molecules so less energy is needed to overcome

  Increases when VDW force increases - large surface area and lots of electrons
• Simple molecular crystals - electrical conductivity

  Can’t conduct electricity

  No charged particles
• Simple molecular crystals - strength

  Weak

  Weak VDW forces between molecules
• What are the giant covalent crystals?

  Diamond

  Graphite

  Graphene
• Ice

  High melting and boiling points - strong hydrogen bonds so lots of energy needed to overcome

  Electrical conductivity - can’t conduct as no charged particles

  Density - less dense than water - water has the same fixed shape - ice has gaps which pushes the water apart