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.

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.

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.

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.

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 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.

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.

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 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.