covalent bonding

• How are covalent bonds formed?

  By atoms sharing electrons
• Which type of atoms form covalent bonds between them?

  Non-metals
• Describe the structure and bonding of a giant covalent substance.

  • Billions of atoms bonded together
  • Strong covalent bonds
• Describe the structure and bonding of small molecules.

  • Small numbers of atoms group together into molecules
  • Strong covalent bonds between atoms
  • Weak intermolecular forces between molecules
• Describe the structure and bonding of polymers.

  • Many identical molecules joined together by strong covalent bonds in a long chain
  • Weak intermolecular forces between the chains
• Why do giant covalent substances have high melting points?

  A lot of energy to break strong bonds
• Why do small molecules have low melting points?

  Weak intermolecular forces require little energy
• Why do larger molecules have higher melting and boiling points than small molecules?

  Larger intermolecular forces require more energy
• Why do most covalent substances not conduct electricity?

  They have no delocalised electrons or ions
• Describe the structure and bonding in graphite.

  • Each carbon atom is covalently bonded to three other carbon atoms, forming layers
  • These layers are held together by weak intermolecular forces.
• Why can graphite conduct electricity?

  It has delocalised electrons between the layers
• Explain why graphite is soft.

  Weak forces between layers allows them to slide
• What is graphene?

  A single layer of graphite
• Give two properties of graphene.

  Very strong and conducts electricity
• What is a fullerene?

  Hollow sphere of carbon atoms
• What is a nanotube?

  Cylindrical molecule of carbon atoms
• Give two properties of nanotubes.

  High tensile strength, conduct electricity/heat
• Give three uses of fullerenes.

  Drug delivery, catalysts, reinforcing composite materials
• What kind of bonds are between atoms?

  Covalent bonds
• What kind of forces are between molecules?

  Weak intermolecular forces
• What type of molecules are joined together in a long chain?

  Many identical molecules
• What kind of bonds join molecules together in a long chain?

  Strong covalent bonds
• Why does it take a lot of energy to break the bonds between the atoms?

  Because they are strong covalent bonds
• Why is only a small amount of energy needed to break intermolecular forces?

  Because they are weak forces
• Are intermolecular forces stronger in large molecules?

  Yes, they are stronger
• Do diamonds have delocalised electrons or ions?

  No, they do not
• In graphite, how many other carbons is each carbon atom bonded to?

  Three
• What shape do carbon atoms arrange in within graphite?

  Hexagonal rings
• How are the hexagonal rings of carbon arranged in graphite?

  In layers
• Does graphite have delocalised electrons?

  Yes, it has delocalised electrons
• How strong are forces between layers in graphite?

  Weak
• What allows electrons to move through graphite?

  Delocalised electrons
• Why can layers of graphite slide over each other?

  Layers are not bonded
• What property does graphite have due to its structure?

  It conducts electricity
• What is a fullerene?

  Hollow cage of carbon atoms
• What shape are fullerene molecules arranged in?

  As a sphere
• What shape is a carbon nanotube?

  Hollow cylinder
• What property do nanotubes have?

  High tensile strength
• What property do nanotubes have relating to electricity?

  They conduct electricity
• What are the applications of fullerenes?

  Lubricants, drug delivery, electronics