Covalent Bonding

Diamond:

• Each carbon atom forms four covalent bonds in a very rigid, giant covalent structure
• Hardest natural substance, so it's used for drill tips
• Pretty and sparkly too.

Graphite:

• Each carbon atom only forms 3 covalent bonds
• This creates layers which are free to slide over each other
• Graphite is soft and slippery too
• Weak intermolecular forces between the layers
• Non - metal - good conductor of heat and electricity
• Each carbon atom has one delocalised (free) electron and its these free electrons which conduct heat and electricity.

Silicon Dioxide (Silica):

• Sand is made of Silica.
• Each grain of sand is one giant structure of silicon and oxygen.