BONDING J

• Ions are made when electrons are transferred 
• When atoms lose or gain electrons to form ions all they are trying do is get a full outer shell like a noble gas. Atoms with a full outer shell are very stable. 
• When non metals form ions they gain electrons into their outer shell to form negative ions.
• When metals form ions they lose electrons from their outer shell to form positive ions 
• Number of electrons lost or gained is the same number as the charge on the ion. If 2 electrons are lost charge is 2+ if 3 electrons are gained charge is -3
• ionic bonding - transfer of electrons , between metal and non metal 
• In ionic bonding metal atoms loses electrons to from positively charged ion and non metal gains these electrons to from a negatively charge ion. 
• These oppositely charged ions are strongly attracted to one another by electrostatic forcer. This attraction is called an ionic bond. 
• Dot and cross diagrams show how ionic bonds are formed 
• Ionic compounds have a regular lattice structure .( giant ionic lattice )
• Ions form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between the oppositely charges inions in all directions in the lattice 
• Ionic compounds all have similar properties 
•   Ionic compounds all have high melting and boiling points due to the strong bonds between ions. It takes lots of energy to overcome this attraction. 

  •   When they are solid the ions are held in place so compounds cannot conduct electricity 
  • when ionic compounds melt the ions are free to move and they’ll carry electric current 
  • Some ionic compounds dissolve easily in water. The ions separate and are all free to move in the solution so they will carry electric current.
• Covalent bonding is sharing electrons 
• Covalent bonding occurs between non metals: when non metal atoms bond together they share pairs of electrons to make covalent bonds. 
• The positively charged nucleus of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces , making covalent bonds very strong.
• You can draw covalent bonds as dot and cross diagrams , displayed formula or 3D models 
• Substances containing covalent bonds usually have simple molecular structures. 
• Atoms within molecules are held together by very strong covalent bonds but the forces of attraction between these molecules are weak intermolecular forces. 
• To melt or boil a simple molecular compound you only need to break these feeble intermolecular forces and not the covalent bonds. So melting and boiling points are very low because molecules are easily parted from each other.  
• Simple molecular compounds do not conduct electricity because they aren’t charged so there is no free electrons or ions. 
• Polymers are long chains or repeating units 
• All atoms in a polymer are joined together by strong covalent bonds.
• The intermolecular forces between polymer molecules are larger than between simple covalent molecules so more energy is needed to break them. This means most polymers a re solid at room temperature 
• The intermolecular forces between polymer molecules are still weaker than ionic or covalent bonds so they have generally low boiling and melting points. 
• Giant covalent structures are macromolecules 
• In giant covalent structures all the atoms are bonded to each other by strong covalent bonds, They have very high melting and boiling points as lots of energy is needed to break the covalent bonds between atoms , they don’t contain charges atoms so don’t conduct electricity not even when molten EXCEPT FROM GRAPHITE 
• Diamond and graphite are made from carbon atoms only. They are allotropes of carbon. 
• Diamond 

  • each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure. 
  • Very hard 
  • The strong covalent bonds take a lot of energy to break so give diamond very high melting and boiling points. 
  • Doesn’t conduct electricity because it has no free electrons or ions 
• Graphite 

  • each carbon atoms forms 3 covalent bonds to create layer of a hexagons. 
  • Each carbon toms has one delocalised electron.
  • They are no covalent bonds between the layers , they are held together weakly so they can slide over each other, this makes graphite soft and slippery , good lubricant 
  • High melting point 
  • Conduct electricity as delocalised electron moles through the structure and carries charge. 
• Graphene is one layer of graphite 

  • sheet of carbon atoms joined together in hexagons. 
  • Sheet is just one atoms thick so is 2D
  • Covalent bonds make it very strong . It is also incredibly light so can be added to composite materials to improve their strength without adding too much weight. 
  • It contains delocalised electrons that move through the structure and carry charge this means it has the potential to be used in electronics as it conducts electricity 
• Silicon dioxide 

  • sometimes called silica , what sand is made of 
  • Each grain of sand is one giant structure of silicon and oxygen 
• Fullerenes from spheres and tubes , they are molecules of carbon. They are mainly made up of carbon atoms arranged in hexagons but can also contain pentagons or heptagons. 
• Buckminsterfullerene was the first fullerene to be discovered. It has molecular formula C60 and from a hollow sphere containing 20 hexagons and 12 pentagons 
• Fullerenes can be used to cage other molecules. They could be used for drug delivery. 
• Fullerenes have a huge surface area so could make great industrial catalysts , they also make great lubricants.
• Metallic bonding involves delocalised electrons 
• Electrons on outer shell of metal atoms are delocalised. There are strong forces of electrostatic attraction between positive metal ions and the shared negative electrons. These forces of attraction hold the atoms together in a regular structure and are known as metallic bonding. Metallic bonding is very strong. 
• Most metals are solids at room temperature. This is because the electrostatic forces between metal atoms and the delocalised sea of electrons are every strong so need lots of energy to be broken. High melting and boiling points. 
• Metals are good conductors of electricity and heat as the delocalised electrons move through the structure and carry charge.