Topic 2 - Bonding, structure, properties

• 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?

  • Held together in a giant lattice
  • Regular structure extending in all directions
  • Electrostatic attraction between positive and negative ions
• What are the properties of ionic substances?

  High melting and boiling points

  
• Why do ionic substances not conduct electricity when solid?

  Because ions are in fixed positions
• When do ionic substances conduct electricity?

  When molten or dissolved in water
• Give an example of a positive ion.

  Na+
• Give an example of a negative ion.

  Cl−
• 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
• What happens during electron transfer in ionic bonding?

  Metal gives away outer shell electrons
• What does Mg become in ionic bonding?

  Mg2+
• What does O become in ionic bonding?

  O2−
• What is a covalent bond?

  A shared pair of electrons between two atoms
• Describe 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

  
• How do intermolecular forces change with molecule size?

  They increase with mass/size of the molecule
• What are polymers?

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

  Polymers that melt/soften when heated
• 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
  • Mostly do not conduct electricity
  • Examples: Diamond, graphite, silicon dioxide

  
• Describe the properties of allotropes of carbon.

  • Diamond: Hard, high melting point, does not conduct
  • Graphite: Soft, high melting point, conducts electricity
  • Fullerenes: Hollow molecules, based on hexagonal rings
  • Nanotubes: Cylindrical, high tensile strength, conducts electricity
  • 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? Why are they harder than pure metals?

  • Alloys: Mixtures of metals with other elements
  • Harder due to different atom sizes distorting layers
• What are the limitations of the simple model?

  No forces between spheres; atoms are not solid spheres
• What does the amount of energy needed to change state depend on?

  Strength of forces between particles
• A pure substance will melt or boil at what temperature?

  A fixed temperature
• What are the three states of matter?

  Solid, liquid, and gas
• What is nanoscience?

  Science studying particles 1 - 100nm in size
• State 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: 2500-10000 nm diameter
• Why do nanoparticles have different properties than bulk materials?

  High surface area to volume ratio