C2 - bonding, structure and properties of matter

• Ions - charged particles made when electrons are transferred.
• • Metals - lose electrons to form positive ions
  • Non-metals - gains electrons to form negative ions
• Ionic bonding - the electrostatic attraction between oppositely charged ions that occurs between positive metal ions and negative non-metal ions.
• Properties of ionic compounds:

  • Giant ionic lattice structure - electrostatic forces of attraction between oppositely charged ions acting in all directions.
  • High melting and boiling points - lots of energy needed to overcome many strong bonds.
  • Conduct electricity only when dissolved or molten - ions free to move and carry electric charge.
• Covalent bonding - a shared pair of electrons between two non-metals, it happens in non-metal compounds and non-metal elements.
• Properties of simple molecular structures:

  • Low melting and boiling points - mostly gases or liquids at room temperature.
  • Don't conduct electricity - there are no charged particles to carry charge.
• As molecules get smaller less energy is needed to break the weaker forces between them.
• Polymers - very long chains of repeating units. They're usually solid at room temperature because they have relatively strong intermolecular forces.
• Giant covalent structures - solids containing atoms which are all bonded to each other by strong confident bonds.

  • High melting and boiling points - lots of energy needed to overcome strong covalent bonds.
  • Don't conduct electricity - no charged particles to carry charge.
• Carbon allotropes

  Each carbon atom in graphite and graphene has one delocalised electron.

  
• Fullerenes - have hollow shapes.
• Nanotubes - cylindrical fullerenes used in nanotechnology, electronics and materials. They have high length to diameter ratios.
• Properties of metals:

  1. High melting and boiling points - lots of energy needed to overcome metallic bonds.
  2. Good thermal conductors - energy transferred by delocalised electrons.
  3. Good electrical conductors - delocalised electrons carry charge.
  4. Soft and malleable - layers in metal slide over each other.
• Alloys - a mixture of metal and at least one other elements. They are harder than pure metals.
• Particle theory

  Particle theory doesn't show the forces between the particles.

  
• Changes of state

  Stronger forces mean higher melting and boiling points.

  
• Melting and boiling:

  substance heats up -> particles gain energy -> forces between particles weaken -> particles break free from position
• Condensing and freezing:

  substance cools down -> particles lose energy -> forces between particles form -> particles held in position
• State symbols:

  • s = solid
  • l = liquid
  • g = gas
  • aq = aqueous