Lesson 7 : Atomic Structures of Diamond and Graphite, with their properties.

Diamond

1. Diamond is a crystalline form of carbon.

2. It has a giant molecular structure

3. Diamond is made up of carbon atoms. Each carbon atom has a 2.4 electronic configuration and needs 4 more electrons to achieve a stable 2.8 electronic configuration of neon. A carbon forms four single covalent bonds with four other carbon atoms to form a giant molecular structure.

4. Each carbon atom is bonded to four other carbon atoms in a tetrahedral arrangement.

Properties of Diamond.

-Hard

Diamond is the hardest known substance.

Due to the strength of the bonding in all directions and its rigid lattice structure, the carbon atoms cannot slide over each other. This strength in bonding and structural rigidity results in its hardness.

-High melting and boiling points

The collective strength of all the covalent bonds within the diamond gives it a very high melting and boiling point as much force is required to overcome these strong electrostatic attractions between diamond molecules.

-Electrical conductivity

Diamond does not conduct electricity as there are no free valence electrons nor mobile ions since they are all used in bonding.

Uses of diamond

Diamonds are rare and precious so they are used as gemstones in jewellery.

Due to its hardness, diamonds are used as tips of drills and other cutting tools.

Graphite

1. Graphite is another crystalline form of carbon.

2. It has a giant molecular structure

3. Graphite has a layered structure, hence it is a good lubricant as there are weak van der waal's forces between the layers.

4. In a layer, each carbon atom is covalently bonded to three other carbon atoms in a hexagonal arrangement to form rings of regular hexagons. Each layer becomes a giant molecule.

5. As each carbon only uses 3 of its 4 valence electrons in bond formation, it still has 1 valence electron which becomes delocalised and mobile, hence it can conduct electricity.

6.The layers of hexagonal rings are held together by weak van der waal's forces of attraction and so the layers can slide over each other.

Properties of Graphite

Hardness.

Graphite is a soft substance as the different layers can slide over each other due to the weak van der waals forces of attraction between them.

High Melting and Boiling Points.

The collective strength of all the covalent bonds within the graph layers give it very high melting and boiling points.

Electrical conductivity.

Graphite conducts electricity parallel to its layered structure due to the free delocalised valence electrons.

Uses of Graphite.

Dry lubricant as it is soft and slippery

Inert electrodes for electrolisis