topic 2

• what are the limitations of the particle model?

  •chemical bonds between particles aren’t represented

  •particles aren’t always spherical and are mostly empty space
• metal ions lose electrons to become positively charged
• non metal ions gain electrons to become negatively charged
• group 1 and 2 elements lose electrons
• group 6 and 7 elements gain electrons
• when are ions formed?

  when atoms gain or lose electrons to have a full outer shell and be stable
• which atoms form ions easier and why?

  atoms that only need 1 or 2 electrons gained or lost because it requires less energy
• what is ionic bonding?

  •transfer of electrons from an atom that needs to lose electrons and one that needs to gain electrons

  •the ions will have opposite charges and are attracted to eachother by electrostatic forces, forming an ionic bond. this forms an ionic compound. between metals and non metals
• what is the structure of an ionic compound?

  each ion is attracted to all those around it, making a regular lattice structure
• what are the properties of an ionic compound?

  •high melting and boiling points

  >lots of strong ionic bonds that require a lot of energy to break

  •can conduct electricity but only when molten or in solution

  >ions are free to move about and carry a charge
• what is covalent bonding?

  •sharing electrons to have a full outer shell

  •non metal atoms
• what is a simple molecular substance?

  •atoms joined by strong covalent bonds

  •individual molecules have weak intermolecular forces

  >only need to break the intermolecular forces to boil or melt the substance

  •can’t conduct electricity

  •e.g - chlorine, ammonia, methane, water
• what is a covalent structure?

  •arranged in regular repeating lattices

  >strong

  •strong covalent bonds

  >high melting and boiling points

  •no weak intermolecular forces as it is only 1 structure

  •don’t conduct electricity (graphite can)

  •e.g - diamond, graphite, silicon dioxide
• what are the properties of diamond?

  •giant covalent structure

  >regular lattice of covalently bonded atoms so strong

  •each carbon is covalently bonded to 4 others making it strong

  >requires lots of energy to break these bonds so high melting point

  •can’t conduct electricity because there’s no free electrons or ions to move around

  •allotrope of carbon
• what are the properties of graphite?

  •each carbon is covalently bonded to 3 others

  •layers of graphene are held together weakly due to no covalent bonds between the layers (hexangol shape). this means the layers can slide over each other making graphite relatively soft

  •high melting point because individual layers are strongly held together

  •each atom has 1 spare electron meaning it can conduct electricity and heat
• what is graphene?

  •layers of graphite

  •can conduct electricity due to delocalised electron

  >makes it useful in electronics

  •tubes and spheres of graphene are fullerenes
• what are uses of fullerenes?

  •medicine - can form spheres around other molecules (e.g drugs) to cage them and then can carry around the body

  •industrial catalysts - large surface area : volume ratio so less material needed than fine particles

  •strengthen other materials because they can add strength without weight

  •nanotubes can be used in nanotechnology and electronics
• what is metallic bonding?

  •bonding between metal atoms

  •atoms share outer shell electrons with all other atoms making them positively charged and leaving a delocalised electron. the electrostatic attraction between the atoms and electrons holds everything together in a regular structure

  •high melting and boiling point

  •can conduct electricity and heat

  •metals are malleable because the layers of the regular structure of pure metals can slide over each other
• what is an alloy?

  •2+ different sizes atoms mixed together to disrupt the regular structure meaning that the layers can’t slide. this makes alloys much harder than pure metals
• how are nanoparticles used in nanomedicine?

  •fullerene delivers drugs

  •research hopes to deliver the drugs directly to the inside of the cells
• how are nanoparticles used in electrical circuits?

  •can make small computer chips
• how are nanoparticles used in medicine?

  •silver nanoparticles have antibacterial properties so are infused in surgical masks and wound dressings
• what are the issues with nanoparticle?

  •they are new so the effects aren’t fully understood yet

  •don’t know what happens when they end up in the sea