Giant Covalent Structures

There are no charged ions.
ALL the atoms are joined up to their adjacent atom by extremely strong covalent bonds and packed into giant regular lattices.
They have very high melting points, since a lot of heat is needed to provide the energy to break apart the many strong covalent bonds.
They tend to be insoluble in water.
They do not conduct electricity.

Diamond

The diamond is the hardest natural substance. It is a form of pure carbon. Each carbon atom forms four covalent bonds to the other carbon atoms. They are arranged in a tetrahedral arrangement. Diamond has a very high melting point, obviously due to very strong carbon-carbon bonds. It does not conduct electricity because all the electrons in the outer levels of the carbon atoms are tightly bonded between the atoms. None of them are free to move around. Diamond is insoluble – like, to both water and other solvents.

Use of Diamond

Saw blades can be tipped with diamonds in high-speed cutting tools used on stone and concrete. The strong tetrahedral structure makes the diamond hard, making it suitable for this purpose.

Graphite

Graphite is arranged differently – it has a layer structure. Each graphite layer is strong, but it is easy to separate individual graphite layers. Each carbon atom only forms three covalent bonds. Graphite conducts electricity because the fourth electron is free to move around.

Use of Graphite

Because of the layered structure, graphite can be used as a dry lubricant to lubricate locks.