giant molecular structure

Solid structure made up of many similar atoms joined by covalent bonds in one dimension (long chains, such as polymers), two dimensions (flat sheets as in graphite, where each layer is a giant molecule), or in three dimensions (such as in diamond and silica).

General properties Giant molecules do not conduct electricity as they have no free electrons as solids and no free ions when molten. They are some of the hardest structures known because of the strong bonds between their atoms. These bonds also give them high melting and boiling points. Graphite, an allotrope of carbon, is an anomaly here as free electrons between its layers enable it to conduct electricity.

Graphite has a layered structure because its atoms form only three covalent bonds. The layers slide over each other, giving graphite a smooth, slippery structure that flakes easily when rubbed against a hard surface. Graphite's unusual properties make it a useful lubricant, and it is also the ‘lead’ used in pencils.

Diamond, like graphite, is an allotrope of carbon. However, its carbon atoms form four covalent bonds in a rigid tetrahedral 3D shape. The covalent bonding between the carbon atoms is very strong, making diamond hard, unreactive, and nonconductive of electricity.