IGCSE Giant Covalent Structures

Graphite can conduct electricity but diamond cannot. Explain why?

Graphite has free electrons which can flow and carry a charge throughout the structure but diamond has no free electrons

How is graphite structured?

In layers

What is another word for giant covalent structures?

Macromolecule

How are the carbon atoms arranged in the diamond structure?

Tetrahedral shape, with each carbon bonded to 4 other carbons

Why can graphite's layers move?

Weak intermolecular forces between the layers that can break and form over and over again.

What do we call the different forms of an element?

allotropes

Why can graphite conduct electricity?

because free electrons can move throughout the structure carrying an electric current.

When you melt or boil a giant covalent structure you have to . . .

break all the very strong covalent bonds

Silicon dioxide has a giant covalent structure very similar to

diamond

The structure of silicon dioxide

each silicon atom is bonded to 4 oxygen atoms, and each oxygen atom is bonded to 2 silicon atoms

Why does diamond have a high melting/boiling point?

has a giant structure with many strong covalent bonds and it requires a lot of energy to break all the bonds

Graphite is used as a lubricant because:

the layers of atoms are attracted to each other by very weak intermolecular forces. These are easy to break, which allows the layers to move and slide across each other - making graphite soft and slippery

Which atoms does graphite and diamond contain?

Carbon only

What can graphite do that diamond and silicon dioxide cannot?

Conduct heat and electricity

How many covalent bonds does each carbon atom form in graphite?

3 covalent bonds the 4th electron of each carbon atom is not used to form a covalent bond - instead it becomes delocalised

How many covalent bonds do carbon atoms make with other carbon atoms in the structure of diamond?

4 covalent bonds

Diamond is much harder than graphite. Why?

Both have a giant covalent structure. Graphite has layers of carbon atoms that can slide over each other easily. In diamond each carbon atom is strongly (covalently) bonded to 4 others. .