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 grains covalent substance

  billons of atoms bonded together by strong covalent bonds
• describe the structure and binding of small molecules

  small numbers of atoms group together into molecules with strong covalent bonds between the atoms and weak intermolecular forces between the molecules
• describe the structure and bonding of polymers

  many identical molecules joined together by strong covalent bonds in a long chain, with weak intermolecular forces between the chains
• why do giant covalent structures have high melting points?

  it takes a lot of energy to break the strong covalent bonds between the atoms
• why do small molecules have low melting points?

  only a small amount of energy is needed to break the weak intermolecular forces
• why do most covalent substances not conduct electricity?

  they don’t have delocalised electrons or ions
• describe the structure and bonding in graphite

  each carbon atom is bonded to three others in hexagonal rings arranged in layers - it has delocalised electrons and weak forces between the layers
• why can graphite conduct electricity?

  the delocalised electron can move
• why is graphite soft?

  layers are not bonded so can slide over each other
• what is graphene?


  one layer of graphite
• what are two properties of graphene?

  strong

  conducts electricity
• what is a fullerene?

  hollow cage if carbon atoms arranged as a sphere or a tube
• what is a nanotube?

  hollow cylinder of carbon atoms
• what are two properties of nanotubes?

  high tensile strength

  conduct electricity
• what are three uses of fullerenes?

  lubricant

  drug delivery (spheres)

  high-tech electrons