C2 - Bonding, Structure and the Properties of Matter

• What type of attraction is ionic bonding?

  Electrostatic attraction
• Why is ionic bonding considered a relatively strong attraction?

  Due to electrostatic forces between ions
• How are ionic compounds held together?

  • 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?

  • High melting and boiling points (strong electrostatic forces).
  • Do not conduct electricity when solid (ions in fixed positions).
  • Conduct when molten or dissolved in water (ions are free to move).
• What is a key consideration when determining the formula of an ionic compound?

  Electrical neutrality
• Why must ionic compounds be electrically neutral?

  Positive and negative charges balance
• What is the definition of a covalent bond?

  Shared pair of electrons
• What are the structure and properties of simple molecular covalent substances?

  • Do not conduct electricity (no ions).
  • Small molecules.
  • Weak intermolecular forces.
  • Low melting and boiling points.
• What happens to intermolecular forces as the mass/size of a molecule increases?

  Intermolecular forces increase
• How does increased molecular mass affect melting/boiling points?

  Melting/boiling points increase
• What are polymers and thermosoftening polymers?

  • Polymers: very large molecules with atoms linked by covalent bonds.
  • Thermosoftening polymers: melt/soften when heated. No bonds between polymer chains. Weak intermolecular forces hold structure solid at room temperature.
• Describe the properties of diamond.

  • Four, strong covalent bonds for each carbon atom.
  • Very hard.
  • Very high melting point.
  • Does not conduct electricity.
• What are the properties of graphite?

  • Three covalent bonds for each carbon atom.
  • Layers of hexagonal rings.
  • High melting point.
  • Layers slide easily due to weak intermolecular forces.
  • Conducts electricity due to delocalised electrons.
• What are the key features of fullerenes?

  • Hollow shaped molecules.
  • Based on hexagonal rings (may have 5/7-carbon rings).
  • C60 has spherical shape (Buckminsterfullerene).
• What are nanotubes and their properties?

  • Cylindrical fullerene with high length to diameter ratio.
  • High tensile strength.
  • Conductivity (delocalised electrons).
• What is graphene?

  Single layer of graphite
• What is metallic bonding?

  Attraction between delocalised electrons and metal ions
• Describe the 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).
• What are alloys and why are they harder than pure metals?

  • Alloys: mixtures of metal with other elements.
  • Different sizes of atoms distort layers, so they can’t slide.
• According to the simple model of matter, what is assumed about interparticle forces?

  No forces exist between spheres
• What affects the energy needed for state changes (solid to liquid or liquid to gas)?

  Strength of forces between particles
• What happens to the melting or boiling point of a pure substance?

  It melts/boils at a fixed temperature
• What happens to the melting or boiling point of a mixture?

  It melts/boils over a range of temperatures
• What are the three states of matter?

  Solid, liquid and gas
• What is nanoscience?

  Science studying 1-100nm particles
• What are some uses of nanoparticles?

  • Medicine (drug delivery systems).
  • Electronics.
  • Deodorants.
  • Sun creams (better skin coverage).
• What is the diameter range of fine particles (soot)?

  100-2500 nm
• What is the diameter range of coarse particles (dust)?

  2500-100000 nm
• Why do nanoparticles exhibit different properties compared to the same materials in bulk?

  High surface area to volume ratio