Giant Covalent Structures (Cambridge O Level Chemistry)

The following table gives information about six substances.

Which substance could be a metal?

State all the substances that are liquid at room temperature.

Which substance could have a macromolecular structure similar to that of silicon(IV) oxide?

Which substance could be propane?

Which substance could be sodium chloride?

Carbon dioxide and silicon(IV) oxide are oxides of Group IV elements.

Complete the following table.

Carbon and silicon are elements in Group IV. They both form oxides of the type XO₂

Silicon(IV) oxide, SiO₂, has a macromolecular structure.

 [3]

 [2]

Explain why the physical properties of carbon dioxide are different from those of diamond and silicon(IV) oxide.

Germanium is an element in Group IV. The electron distribution of a germanium atom is 2 + 8 + 18 + 4. It has oxidation states of +2 and +4.

Germanium forms a series of saturated hydrides similar to the alkanes.

[1]

[1]

Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound germanium(IV) chloride, GeCl₄.

Use o to represent an electron from a chlorine atom.
Use x to represent an electron from a germanium atom.

Describe the structure of the giant covalent compound germanium(IV) oxide, GeO₂.
It has a similar structure to that of silicon(IV) oxide.

Is the change GeCl₂ to GeCl₄ reduction, oxidation or neither? Give a reason for your choice.

The first three elements in Group IV are carbon, silicon and germanium.
The elements and their compounds have similar properties.

The compound, silicon carbide, has a macromolecular structure similar to that of diamond. 

[3]

[2]

Germanium(IV) oxide, GeO₂, has the same macromolecular structure as silicon(IV) oxide. Draw the structural formula of germanium(IV) oxide.

Germanium forms a series of hydrides comparable to the alkanes.

[1]

[2]

The properties of five alkenes at room temperature are shown in Table 1.1

Table 1.1

Answer this question using only the information in the table.

Suggest why the densities of the first three alkenes are much lower than the density of pentene and hexene.

The diagrams show part of the structures of five substances, A, B, C, D and E.

Answer the following question about these structures.

Which one of these structures, A, B, C, D or E, is used in cutting tools? 

Part of the structure of graphite is shown.

Use the information from the diagram to explain why graphite is used as a lubricant.

Separate: Chemistry and Extended Only 

The names of eight substances are given.

 aluminium oxide           calcium oxide       ethanol            nitrogen

                     iron(III) oxide          methane         oxygen         silicon(IV) oxide                   

State which substance is a macromolecular solid.

Carbon is an element which exists in different forms.

Name two forms of the element carbon that have giant covalent structures.

Extended Only 

Magnesium is a metal.

Describe the structure and bonding of metals. Include a labelled diagram in your answer.

It was reported from America that a turbine engine, the size of a button, might replace batteries. The engine would be built  from silicon which has suitable properties for this purpose.

The engine will run on a small pack of jet fuel. What other chemical is needed to burn this fuel?

Silicon has the same type of macromolecular structure as diamond.

[2]

[2]

[1]

Silicon is made by the carbon reduction of the macromolecular compound, silicon(IV) oxide.

SiO₂ + .......... C + → Si + ..........CO

[1]

There are three types of giant structure – ionic, metallic and macromolecular.

Sodium nitride is an ionic compound. Draw a diagram that shows the formula of the compound, the charges on the ions and the arrangement of the valency electrons around the negative ion.

Use x to represent an electron from a sodium atom.
Use o to represent an electron from a nitrogen atom.

Silicon(IV) oxide has a macromolecular structure.

Carbon and silicon are elements in Group IV. Both elements have macromolecular structures.

Diamond and graphite are two forms of the element carbon.

Two of the oxides of these elements are carbon dioxide, CO₂, and silicon(IV) oxide, SiO₂.

The first three elements in Group IV are

   Carbon

   Silicon

   Germanium

The element germanium has a diamond-type structure. Describe the structure of germanium. A diagram is acceptable.

Unlike diamond, graphite is soft and is a good conductor of electricity.

Carbon dioxide and silicon(IV) oxide have similar formulae but different types of structure.