bonding, structure and properties

• properties of metals - strong

  cannot be easily broken due to the strong metallic bonds - e.e electrostatic attraction
• properties of metals - high boiling/ melting points

  requires a lot of energy to break the strong metallic bonds - the greater the number of outer electrons the higher its melting point due to increased positive and delocalised electrons
• properties of metals - good thermal/electrical conductivity

  delocalised electrons carry heat and electric energy from one part of metal to the other due to another as they are free to move
• properties of metal - malleable

  metals can be bent or hammered into different permanent shapes because the electrons move when the metal ions move ions slide over eachother
• properties of metals- ductile

  metals can be stretched into wires metallic bonding stays intact because electrons move when metal ions move
• properties of metal - insoluble in water

  metals don’t dissolve in water as metallic bond is too strong for water to brake it apart
• properties or metal - shiny

  unreacted metals have shiny surface but appear dull when they react with oxygen forming dull metal oxide layer
• covalent structure - diamond

  • pure form of carbon hardest substance known to man
  • does not conduct electricity
  • each carbon atoms forms 4 covalent bonds with 4 other carbon atoms.

  
• covalent structure - graphite

  • layered structures
  • 3 covalent bonds between each carbon atom
  • contains delocalised electrons = good for conducting electricity

  
• covalent bonds


  bonds that form between two or more nonmetal elements
• ion 


  a changed particle, has different numbers of protons and electrons
• ionic bonding


  Bonding between metal and non-metal atoms
• how are ionic bonds formed?


  Electrostatic attraction between positively and negatively charged ions. Transferring from metal to non metal
• giant ionic structure


  ionic compounds form giant ionic lattice,

  oppositely charged ions attract each other

  regular patterns, the strong electrostatic forces of attraction between positive and negative ions keep the bonds together

  
• properties of giant ionic compounds

  High melting and boiling points = strong electrostatic forces require a lot of energy to break the bonds

  Can conduct electricity when dissolved /molten= presence of free ions moving to carry the charge
• covalent bonding


  Bonding between non-metal ions
• what happens in covalent bonding?


  Sharing of electrons to achieve full outer shell as nucleus is attracted to the electrons to hold the molecules together
• metallic bonding


  Bonding of metal atoms
• production of metallic bonds

  metals have giant structures of regularly arranged atoms, electrons from outer shells are delocalised so they share delocalised electrons meaning strong metallic bonds are formed
• allotropes of carbon

  Fullerenes

  bonded to 3 carbons 4th is delocalised

  
• allotropes of carbon

  Graphene

  Single layer of carbon atoms Carbon bonded to 3 others meaning its very strong

  best conductor of electricity known

  
• Allotropes of carbon


  Carbon Nanotubes

  layers of graphite rolled into a cylindrical shape, 3 covalent bonds are formed between each carbon, it’s very strong, good conductor of electricity, soft and slippery to touch

  
• simple molecular structures. atoms held together by covalent bonds, e.g - hydrogen, water, carbon dioxide (low melting/ boiling points + doesn’t conduct electricity)
• Nano scale particle


  particle of the substance with a diameter of between 1nm and 100nm
• Key features of nano scale particle

  Large surface area to volume ratio + good at killing bacteria and viruses (used in deodorant and wound dressings)
• Use of nanoparticles of titanium dioxide


  In sunscreen to block harmful ultraviolet light protecting skin against UV rays
• issues with nano scale particles

  • relatively new = not certain on long term effects
  • particles are so small can easily pass through skin into bloodstream (effect is unknown)
  • can enter environment ( harming and effecting organisms)
• Shape memory alloy (nickel and titanium) 


  regains shape when heated
• shape memory polymer (plastic)


  regains shape when heated
• thermochromic paint 


  changes colour when heated
• photochromic paint 


  changes colour on exposure to light
• polymer gels 


  ability to absorb and expel solvent up to 1000 times their volume