chemistry topic 2

• When does ionic bonding occur?


  Between a non metal and a metal (opposite charged electrons)
• how do groups 1 & 2 form ions?


  They lose electrons to form positive ions as they are metals
• how do groups 6 & 7 form ions?


  They gain electrons to form negative ions as they are non metals
• What is an ionic compound?


  a giant structure of positive and negative ions
• How are ionic compounds structured?


  - Giant ionic lattice

  - Held together by electrostatic forces of attraction between opposite charges
• Do ionic compounds have high or low mpt?


  High

  -> due to strong ionic and electrostatic bonds which require high levels of energy to break.
• Can ionic compounds conduct electricity?


  Yes, when MOLTEN or LIQUID

  Due to ionic lattice being broken and ions are then free to move around
• What are the advantages and disadvantages of a 2D ionic compound diagram?


  AD - Shows arrangement of ions in 1 layer

  DIS - Dosen't show lattice (only 1 layer)
• What are the ads and dis of 3D diagrams (ball and stick)

  AD - Shows arrangement of ions

  DIS - Dosen't show electrostatic forces which act in all directions

  - Show free space between ions which dosen't exist irl lol
• When do covalent bonds form?


  Between non metals

  -> atoms share electrons to make full outershells
• What bonds are formed between the atoms when they covalent bond?


  STRONG covalent bonds

  WEAK intermolecular forces
• What are giant covalent structures?


  Macro-molecules. They have strong covalent bonds.
• What are examples of giant covalent structures?


  - Diamond

  - Graphite/graphene

  - Silicone dioxide
• What are the properties of giant covalent structures?


  High mpt - requires lots of energy to break covalent bonds

  Insoluble in water (DONT dissolve)

  Hard to break (think of diamond)
• What is the structure of diamond?

  Each carbon atom is covalently bonded to 4 other carbons

  -> forms a perfect giant lattice

  -> causes it to have a VERY high mpt

  -> Very hard

  no intermolecular forces
• What is the structure of graphite?


  - Each carbon atom is bonded to 3 other carbon atoms

  - Arranged in flat layers of hexagons

  -> Means they can slide over eachother (makes it soft)
• Why can graphite conduct electricity?


  1 spare carbon atom left unbonded

  -> can move freely & delocalised electrons can conduct electricity
• What is graphene?


  - Single layer of graphite

  - Every 1 carbon is bonded to 3 (can conduct electricity)

  - High mpt due to strong covalent bonds
• What are nanoparticles?


  - Made up of a few hundred atoms

  - between 1 - 100 nm

  - They have a large SA:Volume ratio
• What can nanoparticles be used for?


  Suncream

  Catalysts (high SA)

  cosmetics

  electronics
• What risks come with using nanoparticles?


  - May be breathable due to the very small size

  - Could enter the bloodstream

  - May harm the environment
• What are fullerenes?


  - Large hollow cages

  ->hexagonal rings of carbon joined by covalent bonds

  used to create NANOTUBES
• What is buckminsterfullerine?


  First ever fullerine discovered

  C60

  Slippery and low mpt due to weak intermolecular forces
• What is a nanotube?


  Rolled up sheets of graphene
• What properties do nanotubes have?


  Very strong and not stretchable

  Can conduct electricity - good for electronics.
• What is the structure of metals?


  Lattice of positive charged ions with a sea of delocalised electrons which can conduct electricity
• How are metals bonded?


  Strong metallic bonds - high mpt
• Why can metals be bent into shapes?


  - Layers of ions can slide over eachother
• What are alloys?


  - Mixture of metals

  - Different sized metal atoms disrupt the sliding layers making the metal stronger and harder
• what is an ionic compound

  • giant lattice of ions
• what are the melting and boiling points of small molecules?

  • low due to weak intermolecular forces which are easy to break
• can small molecules conduct electricity

  • NO
  • because they have no free electrons
• what are the differences between covalent bonds and IMF

  • CB - found between the atoms
  • IMF - found between the molecules
• how is graphite bonded

  • strong covalent bonds between atoms
  • very weak imfs between layers
• what are the properties of graphene

  • transparent -absorbs visible light
  • one atom thick
  • very very very strong
  • flexible
• what is a fullerene

  • hollow tube or sphere
  • rings of 5,6,7 carbon atoms
• what are fullerenes used for

  • drug delivery system - can trap other molecules
  • can trap catalysts on their surface and easily catalyse a reaction due to large SA
• what is buckminsterfullerene

  • made of 60 carbon atoms to join 20 hexagons
• what is a nano tube

  • layer of graphene rolled into a tube