bonding and structure properties and matter

• what is ionic bonding?


  • ionic bonding is the electrostatic attraction between positive and negative ions
  • it is a relatively strong attraction
• how are ionic compounds held together?

  • they are held together in a giant lattice.
  • it's a regular structure that extends in all directions in a substance.
  • electrostatic attraction between positive and negative ions holds the structure together.
• state properties of ionic substances

  • high melting and boiling points (strong electrostatic forces between oppositely charged ions)
  • do not conduct electricity when solid (ions in fixed positions)
  • conduct when molten or dissolved in water - ions are free to move.
• give 5 examples of positive ions and 5 examples of negative ions

  • positive: NA+, Mg2+, Al3+, Ca2+, Rb+
  • negative: Cl-, Br-, SO42-, NO3-, OH- (chloride, bromide, sulfate, nitrate, hydroxide)
• how are ionic compounds formed? explain in terms of MgO case.

  • reaction of a metal with a non- metal
  • electron transfer occurs - metal gives away its outer shell electrons to non- metal.
  • Mg is in group 2, so has 2 available outer shell electrons
  • O is in group 6, so can accept 2 electrons to get a full outer shell configuration
  • Mg becomes Mg2+ and O becomes O2-
• what is a covalent bond?

  • covalent bond is a shared pair of electrons between two atoms.
• describe the structure and properties of simple molecular covalent substances

  • do not conduct electricity
  • small molecules
  • weak intermolecular forces, therefore:
  • low melting and boiling points
• how do intermolecular forces change as the mass/ size of the molecule increases?

  • they increase. That causes melting/ boiling points to increase as well (more energy needed to overcome these forces)
• what are polymers? 


  • polymers are very large molecules with atoms linked by covalent bonds.
• what are giant covalent substances? give examples

  • solids, atoms covalently bonded together in a giant lattice.
  • high melting/ boiling points - strong covalent bonds
  • mostly don't conduct electricity ( no delocalised e-)
  • diamond, graphite
• describe the properties of diamond

  • four strong covalent bonds for each carbon atom
  • very hard, strong bonds
  • very high melting point (strong bonds)
  • does not conduct ( no delocalised electrons)
• describe the properties of graphite

  • three covalent bonds for each carbon atom
  • layers of hexagonal rings
  • high melting point
  • layers free to slide as weak intermolecular forces between layers; soft, can be used as a lubricant - conduct thermal and electricity due to one delocalised electron per each carbon atom
• describe the properties of fullerenes

  • hollow shaped molecules
  • based on hexagonal rings but may have 5/7 carbon rings
  • C60 has spherical shape, simple molecular structure ( Buckminsterfullerene)
• describe the properties of nanotubes?

  • cylindrical fullerene with high length to diameter ratio
  • high tensile strength
  • conductivity
• describe the properties of graphene

  • a single layer of graphite.
• what is metallic bonding?

  • forces of attraction between delocalised electrons and nuclei of metal ions.
• describe properties of metals

  • high melting/ boiling points ( strong forces of attraction)
  • good conductors of heat and electricity ( delocalised electrons)
  • malleable, soft ( layers of atoms can slide over each other whilst maintaining the attraction forces)
• what are alloys? why are they harder than pure metals?

  alloys:

  • mixtures of metal with other elements, usually metals
  • different sizes of atoms distorts the layers, so they can't slide over each other, therefore alloys are harder than pure metals
• what does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?

  • the strength of the forces between the particles of the substance. The nature of particles involved depends on the type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance.
• a pure substance will melt or boil at?

  • a fixed temperature
  • a mixture will melt over a range of temperatures.
• what are the three states of matter?

  • solid, liquid and gas
• state the uses of nanoparticles

  • medicine
  • electronics
  • deodorants
  • sun creams
• why do nanoparticles have properties different from those for the same materials in bulK?

  high surface area to volume ratio