Covalent Bonding (Edexcel GCSE Chemistry)

An oxygen molecule, O₂, is formed when two oxygen atoms covalently bond together.

How many electrons need to be shared between these two oxygen atoms?

Hydrogen, carbon, oxygen and chlorine can all form covalent bonds by sharing electrons.

How many electrons does each element need to share in order to complete its outer shell?

Figure 1 shows the displayed structure of ethanol 

Complete the dot and cross diagram in Figure 2 to show the bonding in ethanol. Show the outer shell electrons only.

Ethanol has a boiling point of 79 °C. Explain why ethanol has a low boiling point.

Explain, in terms of particles, why ethanol does not conduct electricity.

Methane and water are both simple molecules containing covalent bonds.

Which statement is not correct?

This question is about substances with covalent bonds.

i) Draw a dot and cross diagram to show the outer shell electrons in a molecule of nitrogen, N₂

(2)

ii) Describe the forces of attraction in a covalent bond.

(2)

The diagram shows three different structures of carbon. 

Structure A	Graphite	C60 Fullerene

i) Name structure A.

(1)

ii) Graphite and C₆₀ fullerene contain covalent bonds, but have different structures.

Explain why C₆₀ fullerene has a much lower melting point than graphite.

Refer to structure and bonding in your answer.

(4)

Carbon dioxide contains covalent bonds.

The covalent bonds in a molecule of carbon dioxide can be represented by a dot-and-cross diagram.

Which is the correct dot-and-cross diagram for carbon dioxide?

☐	A
☐	B
☐	C
☐	D

Sulfur can form covalent bonds.

Complete the dot and cross diagram in Figure 1 to show the covalent bonding in a molecule of hydrogen sulfide.

Show the outer shell electrons only.

Which of the following set of properties is most likely to be hydrogen sulfide?

The atoms in carbon dioxide are held together by covalent bonds.

Describe the forces of attraction in a covalent bond.

Diamond is made up of carbon atoms.

Figure 1 shows the structure of diamond.

The black dots represent the carbon atoms.

The lines represent bonds.

Figure 1

Name the type of bonding in diamond.

Explain why each carbon atom forms four bonds.

Carbon can also form compounds like methane (CH₄).

Draw a dot and cross diagram to show the bonding in methane.

Show the outer electrons only.

The melting point of diamond is around 4500°C.

The melting point of methane is -182°C.

Explain this difference using your knowledge of bonding.

Ethanoic acid is the acid found in vinegar.

Figure 1 shows the dot and cross structure of ethanoic acid.

Figure 1

State what each dot and cross represents.

Complete Figure 2 to show the structure of an ethanoic acid molecule.

Use a single line to show each bond.

Figure 2

Determine the empirical formula of ethanoic acid.

The boiling point of ethanoic acid is 118°C.

The boiling point of water is 100°C.

Use your knowledge of bonding to suggest a reason for the difference.

An atom has a length of 0.1 nm.
A grain of sand has a length of 1 mm.
1 mm = 1 million nm

Calculate how many atoms could line up next to each other on a grain of sand.

Calculate the order of magnitude between the length of an atom and a grain of sand.

Atoms bond together to form molecules.

Show the bonding in a chlorine molecule. Only include the electrons in the outer shell.

Chlorine is found in Group 7 of the Periodic Table. All elements in Group 7 form molecules with two atoms.

Explain how the size of the molecule changes as you go down Group 7.

Figure 1 shows the structure of hydrogen peroxide.

Figure 1

The lines represent covalent bonds.

Explain why hydrogen peroxide contains covalent, not ionic bonds.

Calculate the relative formula mass of hydrogen peroxide.

(M_r H = 1, M_r O = 16)

Complete Figure 2 to show the dot and cross diagram for hydrogen peroxide.

Figure 2

A student said ‘Covalent bonds only exist between atoms of different elements’.

Use an example to show that this statement is incorrect.

This question is about trends in the sizes of atoms.

Group 0 of the Periodic table contains the noble gases.

i) Predict how the size of the atoms changes as you go down Group 0.

 [1]

ii) Explain your answer to part i)

[1]

Figure 1 is a graph that shows how the length of atoms changes as you go across Period 3 of the Periodic Table.

Figure 1

i) Describe what the graph shows.

[1]

ii) Suggest a reason for this trend.

[3]

Group 7 contains the halogens.

Hydrogen reacts with halogens to form simple covalent molecules called hydrogen halides.

Draw a dot cross diagram to show the bonding in the molecule formed when hydrogen reacts with chlorine

Higher Tier Only

Figure 2 shows the bond energies in hydrogen halides.

Figure 2

Suggest an explanation for the trend shown in Figure 2.