Topic 2- bonding, structure and the properties of matter

• What is ionic bonding?

  Electrostatic attraction between positive and negative ions
• How strong is the attraction in ionic bonding?

  It is a relatively strong attraction
• How are ionic compounds held together?

  In a giant lattice structure
• What extends in all directions in ionic compounds?

  A regular structure of ions
• What holds the structure of ionic compounds together?

  Electrostatic attraction between ions
• What are the properties of ionic substances?

  • High melting and boiling points
  • Do not conduct electricity when solid
  • Conduct electricity when molten or dissolved
• What is important when working out a formula of an ionic compound?

  Positive and negative charges must balance
• How are ionic compounds formed?

  Through the reaction of a metal with a non-metal
• In the case of MgO, what happens during ionic compound formation?

  Electron transfer occurs from metal to non-metal
• How many outer shell electrons does magnesium have?

  Two outer shell electrons
• How many electrons can oxygen accept to achieve a full outer shell?

  Two electrons
• What is a covalent bond?

  A shared pair of electrons between atoms
• How do intermolecular forces change with molecule size?

  They increase with larger molecules
• Describe the structure and properties of simple molecular covalent substances.

  • Do not conduct electricity (no ions)
  • Composed of small molecules
  • Weak intermolecular forces
  • Low melting and boiling points

  
• What are polymers?

  Very large molecules linked by covalent bonds
• What are thermosoftening polymers?

  Polymers that melt when heated
• Why do thermosoftening polymers melt when heated?

  Weak intermolecular forces are overcome
• Describe the properties of allotropes of carbon.

  • Diamond: Hard, high melting point, non-conductive
  • Graphite: Soft, high melting point, conductive
  • Fullerenes: Hollow molecules, based on hexagonal rings
  • Nanotubes: High tensile strength, conductive
  • Graphene: Single layer of graphite
• What is metallic bonding?

  Attraction between delocalised electrons and metal ions
• Describe properties of metals.

  • High melting/boiling points
  • Good conductors of heat and electricity
  • Malleable and soft
• What are alloys and why are they harder than pure metals?

  • Alloys: Mixtures of metals with other elements
  • Harder due to distorted layers preventing sliding
• What does the energy needed to change state depend on?

  Strength of forces between particles
• At what temperature does a pure substance melt or boil?

  At a fixed temperature
• What are the three states of matter?

  Solid, liquid, and gas
• What is nanoscience?

  Study of particles 1 - 100nm in size
• What are the uses of nanoparticles?

  • Medicine (drug delivery systems)
  • Electronics
  • Deodorants
  • Sun creams (better skin coverage)
• What are fine and coarse particles?

  • Fine particles: 100-2500 nm diameter
  • Coarse particles: 2500-105 nm diameter
• Why do nanoparticles have different properties than bulk materials?

  High surface area to volume ratio