C2

• What is ionic bonding?

  Ionic bonding is the electrostatic attraction between positive and negative ions.
• Why is ionic bonding considered a relatively strong attraction?

  Because it involves the electrostatic attraction between oppositely charged ions.
• How are ionic compounds held together?

  • They are held together in a giant lattice.
  • It’s a regular structure that extends in all directions.
  • Electrostatic attraction between positive and negative ions holds the structure together.

  
• What are the properties of ionic substances?

  Ionic substances have high melting and boiling points, do not conduct electricity when solid, and conduct when molten or dissolved in water.
• Why do ionic substances not conduct electricity when solid?

  Because the ions are in fixed positions and cannot move.
• What happens to ionic substances when they are molten or dissolved in water?

  The ions are free to move, allowing them to conduct electricity.
• Give five examples of positive ions.

  Na+, Mg2+, Al3+, Ca2+, Rb+
• Give five examples of negative ions.

  Cl−, Br−, SO4 2−, NO3 −, OH−
• What is important when working out the formula of an ionic compound?

  The compound must be electrically neutral, meaning positive and negative charges balance each other.
• How are ionic compounds formed? Explain using the example of MgO.

  • Reaction of a metal (Mg) with a non-metal (O).
  • Electron transfer occurs; metal gives away outer shell electrons to non-metal.
  • Mg becomes Mg2+ and O becomes O2− (oxide).
• What is a covalent bond?

  A 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 (no ions).
  • Composed of small molecules.
  • Weak intermolecular forces lead to low melting and boiling points.

  
• How do intermolecular forces change as the mass/size of the molecule increases?

  Intermolecular forces increase, causing melting and boiling points to increase as well.
• What are polymers and thermosoftening polymers?

  • Polymers are very large molecules with atoms linked by covalent bonds.
  • Thermosoftening polymers melt/soften when heated due to no bonds between polymer chains.

  
• What are giant covalent substances? Give examples.

  • Solids with atoms covalently bonded in a giant lattice.
  • High melting/boiling points due to strong covalent bonds.
  • Examples: Diamond, graphite, silicon dioxide.

  
• Describe and explain the properties of allotropes of carbon.

  • Diamond: Strong covalent bonds, very hard, high melting point, does not conduct electricity.
  • Graphite: Three covalent bonds per carbon atom, layers of hexagonal rings, high melting point, conducts electricity due to delocalised electrons.
  • Fullerenes: Hollow molecules based on hexagonal rings.
  • Nanotubes: Cylindrical fullerenes with high tensile strength and conductivity.
  • Graphene: A single layer of graphite.
• What is metallic bonding?

  Metallic bonding is the attraction between delocalised electrons and the nuclei of metal ions.

  
• Describe properties of metals.

  • High melting/boiling points due to strong forces of attraction.
  • Good conductors of heat and electricity due to delocalised electrons.
  • Malleable and soft; layers of atoms can slide over each other.
• What are alloys and why are they harder than pure metals?

  • Alloys are mixtures of metals with other elements.
  • Different sizes of atoms distort the layers, preventing them from sliding over each other, making alloys harder than pure metals.
• What are the limitations of the simple model of atoms?


  The simple model does not account for forces between spheres and incorrectly depicts atoms, molecules, and ions as solid spheres.
• What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?

  It depends on the strength of the forces between the particles of the substance.
• At what temperature will a pure substance melt or boil?

  A pure substance will melt or boil at a fixed temperature.
• What are the three states of matter?

  Solid, liquid, and gas.
• What is nanoscience?

  Nanoscience is the science that studies particles that are 1 - 100 nm in size.
• State the uses of nanoparticles.

  • Medicine (drug delivery systems)
  • Electronics
  • Deodorants
  • Sun creams (better skin coverage and more effective protection against cell damage)
• What are fine and coarse particles?

  • Fine particles (soot): 100-2500 nm diameter.
  • Coarse particles (dust): 2500-10,000 nm diameter.
• Why do nanoparticles have properties different from those for the same materials in bulk?

  Because they have a high surface area to volume ratio.
• Why are fullerenes such good conductors of electricity?

  Fullerenes have a sea of delocalised electrons which can easily move thoughout the fullerene