Nano-scale Particles

Nano-scale Particles

Properties of Metals

  • Metals are typically hard, shiny, malleable, ductile, and conductive of heat and electricity.
  • They show a tendency to lose electrons in chemical reactions, forming positive ions known as cations.
  • Metallic bond arise from the attraction between cations and a ‘sea’ of delocalised electrons.

Properties of Ionic Compounds

  • Ionic compounds consist of a regular lattice structure of ions with strong electrostatic forces of attraction.
  • They have high melting and boiling points due to the large amounts of energy required to break these bonds.
  • When dissolved or molten, ionic compounds can conduct electricity as the ions are free to move.

Properties of Covalent Substances

  • Covalent substances can be simple molecules like carbon dioxide and water, or giant structures like diamond and silica.
  • Most simple molecular substances have relatively low melting and boiling points and do not conduct electricity.
  • Giant covalent substances, on the other hand, have very high melting and boiling points due to strong covalent bonds in their lattice structures.
  • Diamond, graphite, and graphene are all examples of substances that exhibit covalent bonding.

Structures of Ionic Compounds

  • Ions in an ionic compound are held together in a lattice structure by strong ionic bonds.
  • In an ionic lattice, each ion is surrounded by ions of the opposite charge, which maximises the attraction between ions.

Forming Covalent Bonds

  • Covalent bonds are formed by the sharing of one or more pairs of electrons between two atoms.
  • Each atom involved in the bond provides one or more of the shared electrons.

Intermolecular Bonding

  • Intermolecular forces are the forces of attraction that exist between molecules.
  • These forces are weaker than either ionic or covalent bonds.
  • The strength of intermolecular forces determines the state of matter, boiling points, and melting points of most molecular substances.

Properties of Diamond, Graphite, Fullerenes, Carbon Nanotubes, and Graphene

  • Diamond is hard and has a high melting point due to the strong covalent bonds in its tetrahedral structure.
  • Graphite has layered sheets of carbon atoms with weaker interlayer forces, allowing layers to slide over each other.
  • Fullerenes possesses hollow structures which makes them useful in delivering drugs in medicine.
  • Carbon nanotubes are cylindrical fullerenes with very high tensile strength thus they are used in electronics and nanotechnology.
  • Graphene is a single layer of graphite and is extremely strong for its weight.

Individual Atoms and Bulk Materials

  • Properties observed in a bulk material may not be present in individual atoms of the same element.
  • The bulk properties are collective, emerging from the interaction of many atoms or molecules.

Nano-scale Particles

  • Nano-scale particles have a large surface area to volume ratio which gives them unique properties.
  • The reactivity of nanomaterials is significantly higher compared to that of the same materials in bulk form.