AQA GCSE Chemistry Foundation (8462), Foundation tier · Bonding, structure and the properties of matter › Structure and bonding of carbon
Practise Diamond. 6 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Diamond is a form of carbon with a giant covalent structure in which each carbon atom is bonded to four others. You must explain why it is very hard, has a very high melting point and does not conduct electricity. It often appears alongside graphite in comparison questions.
Key facts
Diamond: carbon atoms, each forming 4 covalent bonds
Giant covalent structure: a rigid 3D network
Very hard: strong covalent bonds hold every atom rigidly
Very high melting point: many strong covalent bonds to break
Does not conduct: no delocalised electrons (all 4 outer electrons used in bonds)
Notes
Structure and bonding
diagram
Diamond is made of carbon atoms only.
Each carbon atom forms four covalent bonds with four other carbon atoms.
This makes a giant covalent structure: a rigid 3D network that continues in all directions, with no separate molecules.
Diamond: every carbon atom is bonded to four others in a rigid 3D network.
A carbon atom has four outer electrons, and in diamond all four are used in covalent bonds.
Properties explained
Very hard: every atom is held in place by strong covalent bonds in a rigid 3D network, so the atoms cannot easily be moved out of position.
Very high melting point: to melt diamond, a huge number of strong covalent bonds must be broken, which needs a very large amount of energy.
Does not conduct electricity: all the outer electrons are used in bonds, so there are no delocalised electrons (and no ions) free to move and carry charge.
Uses and comparison
Its hardness makes diamond useful for cutting tools, such as the tips of drills and saws used to cut rock, glass and metal.
Graphite is also carbon with a giant covalent structure, but each atom forms only three bonds. This one difference explains why graphite is soft and conducts electricity.
How to answer each type of question
Explain why diamond has a very high melting point (or is very hard)
3 marksGrade 5
Describe the structure: giant covalent, each carbon atom bonded to four others.
Say there are many strong covalent bonds.
Melting point: a lot of energy is needed to break them. Hardness: the atoms are held rigidly in place.
Example. Explain why diamond has a very high melting point.
Show the model answerHide the model answer
Diamond has a giant covalent structure in which each carbon atom is bonded to four others (1). There are many strong covalent bonds (1). A lot of energy is needed to break these bonds (1).
Don’t lose marks
Saying diamond is made of molecules or has intermolecular forces.
Saying diamond is hard because of ionic bonds, or because of 'strong forces' without saying covalent bonds.
Saying diamond doesn't conduct because it has no free ions. The key point is that it has no delocalised electrons.
Writing that each carbon atom in diamond forms three bonds. That is graphite.
More tips
Memory tricks
Diamond: 4 bonds per carbon = 0 spare electrons = no conduction.
Hard, high, no flow: diamond is very hard, has a very high melting point, and lets no charge flow.
Diamond vs graphite: 4 bonds vs 3 bonds. Almost every difference in properties comes from this.
Exam technique
Start every diamond answer with the structure: giant covalent, each carbon atom bonded to four others. Then link each property to it.
Use 'many strong covalent bonds' for hardness and melting point, and 'no delocalised electrons' for conductivity.
In comparisons with graphite, write about both substances, point by point.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State that diamond is a form of carbonDiamond is made only of carbon atoms, in a giant covalent structure.
Grade 4
Describe the bonding in diamondEach carbon atom forms four covalent bonds with other carbon atoms.
Grade 5
Explain why diamond is very hardMany strong covalent bonds hold the atoms rigidly in a 3D network.
Grade 5
Explain diamond's very high melting pointA lot of energy is needed to break the many strong covalent bonds.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
How many covalent bonds does each carbon atom form in diamond?
4
Diamond burns when it is heated strongly in oxygen. Name the product.
carbon dioxide
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Diamond is a form of carbon.
(a) How many covalent bonds does each carbon atom form in diamond?[1]
(b) Diamond is used in the tips of drills. Which property makes diamond suitable for this use? Tick (✓) one box.[1]
It is very hard.
It conducts electricity.
It is shiny.
It dissolves in water.
(c) Why does diamond not conduct electricity? Tick (✓) one box.[1]
It has no delocalised electrons.
It has no covalent bonds.
Its molecules are too small.
Its ions cannot move.
(d) What type of structure does diamond have?[1]
Show the answer and mark scheme
(a)Answer: 4
4
(b)Answer: It is very hard.
(c)Answer: It has no delocalised electrons.
(d)Answer: giant covalent
giant covalent
Question 2Medium6 marks
Diamond is a form of carbon.
(a) Explain why diamond is very hard.[2]
(b) Explain why diamond has a very high melting point.[2]
(c) Explain why diamond does not conduct electricity.[2]
Show the answer and mark scheme
(a)Answer: Each carbon atom is joined to four others by strong covalent bonds in a rigid three-dimensional structure.
each carbon atom is bonded to four other carbon atoms by strong covalent bonds
(in a) rigid / 3D giant structure
(b)Answer: There are many strong covalent bonds, which need a lot of energy to break.
many strong covalent bonds
a lot of energy is needed to break them
(c)Answer: All four outer electrons of each carbon atom are used in covalent bonds, so there are no delocalised electrons.
all four outer electrons (of each carbon atom) are used in covalent bonds
so there are no delocalised electrons / charged particles free to move