CH 2a) Covalent substances / allotropes of carbon

• Conductivity of simple molecules

  Don't conduct electricity in any state. No free electrons so nothing to carry charge
• Mpt and bpt of simple covalent

  Low. Intermolecular forces are weak so doesnt take much energy
• Trends in Mpt and bpt covalent

  Bigger molecule stronger IM forces -> more energy needed
• What is a polymer

  long chain of monomers. Consists of long molecules made of repeating sections. All atoms in a polymer joined by strong covalent bonds.
• Mpt and bpt of polymers

  Higher than simple covalent substances bc stronger IM forces
• What is a giant covalent structure

  huge number of atoms held together by a network of covalent bonds
• Mpt and bpt of giant covalent structures

  High. Need to overcome strong covalent bonds between atoms
• How many bonds does each carbon form for diamond

  4
• How many bonds does each carbon form for graphite and what does this mean

  3. 1 delocalised electron per carbon atom that can carry charge
• What's silicon dioxide


  What sand is made of. 1 grain of sand = one giant structure of silicon and oxygen
• Properties of diamond and explain

  -very hard, each carbon forms 4 covalent bonds -high mpt. Strong covalent bonds need a lot of energy to break-doesn't conduct electricity. No delocalised electrons
• Properties of graphite and explain

  -soft and slippery- no covalent bonds between layers so they can easily slide over each other-high melting point, covalent bonds within layers require a lot of energy to break-conducts electricity, each carbon atom forms 3 bonds so has an electron that's delocalised
• What is graphene

  A single layer of graphite
• Properties of graphene and explain. Uses

  Very strong bc network of covalent bonds. Light so can be added to materials to improve their strength without adding much weight. Conducts electricity because of delocalised electrons so can be used in electronics
• What are fullerenes


  Molecules of carbon atoms with hollow shapes
• What shapes are fullerenes made from

  Mainly carbon arranged in hexagons but also pentagons and heptagons
• What are fullerenes used for

  To 'cage' other molecules by forming its structure around another atom or molecule, which is then trapped inside.-could be used in medicine to deliver a drug into the body-have a huge surface area so could make industrial catalysts. Individual catalyst molecules could be attached to the fullerene. -good lubricants
• What are nanotubes

  Tiny carbon cylinders
• Ratio between diameter and length of nanotubes.

  Very high
• Conductivity of nanotubes?

  Good conductors of electricity and heat
• Tensile strength of nanotubes?

  High tensile strength
• Nanotechnology

  Use of nanotubes. Electronics or to strengthen material
• Buckministerfullerene

  first fullerene to be discovered, formula C60, hollow sphere