Chemistry

Graphite

• Made from carbon only

• Each carbon atom makes 3 covalent bonds to other atoms forming layers. The layers are only held together by weak forces, so slide over one another easily. So graphite feels soft and slippery.

• One electron from each carbon atom can move through the structure- it is delocalised. So graphite can conduct electricity.

Silicon Dioxide (Silica)

• Made from silicon and oxygen
• Each silica atom makes 4 covalent bonds to oxygen atoms
• Each oxygen makes 2 covalent bonds to silicon atoms
• High melting point
• Hard and strong

Metallic Structures 

• Strong forces of attraction (electrostatic forces) between the positively charged metal ions and the negatively charged sea of electrons hold the structure together 

• The outer electrons from each atoms are delocalised- they can move through the structure forming a sea of electrons that hold the metal ions together. 

• Metals conduct electricity because the outer electrons from each atom are delocalised so they can move through the structure.

• Metals are malleable because the layers of atoms can easily slide over one another

• Metals have a high melting point because there are strong forces forces of attraction between the molecules. So a large amount of energy is required to overcome these forces and melt the metal.

• The three types of bonding

• Covalent = non-metals only
• Ionic= a metal with a non-metal
• Metallic=Metal only