properties of materials c3

• what does the period in the periodic table tell you?


  number of shells (which contain outer electrons)
• what happens in a chemicak reaction?

  no atoms are made or destroyed
• what are properties of fullerenes?


  weak intermolecular bonds but string covalent bonds
• what are properties of giant covalent structures? (diamond)


  .they are hard as they have strong covalent bonds

  • high mp + bp as lots of energy needed to break these bonds
  • no intermolecular forces - as has no molecules
• why does diamond have a high mp + bp??

  the four covalent bonds are are strong and extend in a giant lattice , so a lot of energy is needed to break the lattice.
• why does diamond not conduct electricty?

  no delocalised electrons
• why is diamond hard?

  it has strong covalent bonds
• why is graphene strong?

  strong covalent bonds
• how many bonds does carbon make in graphite?

  3, forming layers of hexagons
• why is graphite soft and slippery ?

  .the layers are attracted to each other by weak intermolecular forces, and the layers can slide over each other
• why does graphite have a high melting point?

  strong covalent bonds
• why are there no covalent bonds between layers of graphite?

  they are only held together weakly so they’re free to move over each other
• why does graphite conduct electricity?

  has delocalised electrons
• why does graphite have a high melting point?

  Covalent bonds in the layers require energy to break
• graphine has strong covalent bonds inside layers
• what are polymers made up of?

  covalently bonded carbon chains
• what are the properties of simple molecular substances?

  have strong covalent bonds inside molecules

  but weak intermolecular forces, as little energy is required to break intermolecular forces, not the covalent bonds (hence why is has a low mp/bp)

  • don’t conduct electricity - no delocalised electrons
• what is covalent bonding?

  a shared pair of electrons between 2 atoms
• why do ionic compounds dissolve easily in water?

  the ions separate and are free to move in the solution
• why are alloys harder than pure metals??

  In the alloy, the atoms of different size and the layers in an alloy are distorted, all the layers slide over each other less easy than in the pure metal
• why don’t ionic compounds conduct electricity?

  because the ions are in a fixed position and can’t move - can only move and conduct when melted
• why do ionic compounds have a high mp/bp?

  due to the Strong electrostatic attractions between ions which require a lot of energy to break
• in ionic bonding, when a metal + non metal react,

  * the metal atom loses electrons to form a positive ion (cation)

  * the non metal gains electrons to form a negative ion (anion)

  these oppositely charged ions are strongly attracted by electrostatic forces
• how did Rutherford describe atoms?

  having a tiny, dense, and positively charged core called the nucleus gold foil experiment : fired positively charged alpha particles that a thin sheet of gold: the particles passed through the foil as most of the atom is empty Space but a small number of particles were deflected backwards because they hit the nucleus.
• how did JJ thompson describe the atom?

  Plum pudding model- showed that all atoms contain tiny negatively charged particles or electrons. 
• what groups in the periodic table are most likely to form ions?

  group 1 + 2 - are metals - they lose electrons to form positive ions

  grouo 6+7 - are non metala - they gain electrons to form negative ions
• when atoms lose or gain electrons, it means they’re trying to get a full outer shell
• what structure do ionic compounds have?

  giant ionic lattice
• why do metals conduct electricity ?

  .because they have negative delocalised electrons
• what hold the atom together in metals?

  that are strong forces of electrostatic attraction between the positive ions and negative electrons - these forces of attraction hold the atom together in a metallic bond
• why are metals malleable ?

  .because layers of ions can slide over each other
• why do metals conduct electricity ?

  they conduct electricity because the delocalised electrons carry electrical charge and heat energy through the material