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

Diamond and graphite are both allotropes of carbon.

State what is meant by the term allotrope.

Silicon(IV) oxide, SiO₂, has a similar structure to diamond.

State the type of structure found in both diamond and silicon(IV) oxide.

Complete the sentence about covalent bonding.

A covalent bond is formed when two atoms _____________ a pair of _____________.

State three physical properties that are similar for both diamond and silicon(IV) oxide.

The diagram below shows the structure of silicon(IV) oxide.

(a) Identify the feature that shows silicon(IV) oxide has a giant covalent structure. [1]

(b) Explain why the formula is written as SiO₂. [2]

(c) Each oxygen atom forms covalent bonds. State how many bonds. [1]

Draw a diagram to show the bonding in a diamond structure. Your diagram should clearly show:

• At least 5 carbon atoms
• The bonds between atoms
• The tetrahedral arrangement around each carbon

A student writes: "Diamond is made of carbon molecules bonded together."

Explain what is wrong with this statement and write a correct version.

Explain why diamond has a very high melting point.

Diamond does not conduct electricity.

Explain why diamond does not conduct electricity.

Silicon(IV) oxide is used in sandpaper.

Suggest why silicon(IV) oxide is suitable for this use.

A student investigates the hardness of different substances by attempting to scratch them with a steel nail.

Explain why diamond is harder than graphite, even though both are forms of carbon.

Diamond and silicon(IV) oxide are both giant covalent structures.

Compare the structure and bonding in diamond and silicon(IV) oxide.

A company wants to choose between diamond and silicon(IV) oxide for cutting tools.

Diamond costs £2000 per gram. Silicon(IV) oxide costs £0.50 per gram.

Using your knowledge of structure and bonding, evaluate which material would be better for industrial cutting tools. Justify your answer.

Extended Response - Plan and Write

Explain why substances with giant covalent structures have very high melting points and do not conduct electricity.

In your answer you should:

• Describe the structure of giant covalent substances
• Explain the relationship between structure and melting point
• Explain the relationship between structure and electrical conductivity
• Use diamond or silicon(IV) oxide as an example