Covalent Bonding (Edexcel GCSE Combined Science: Chemistry): Exam Questions

Covalent substances can be simple molecular covalent or giant covalent.

i) Ammonia is a simple molecular, covalent substance. Which is the most likely set of properties for ammonia?

(1)

ii) Ammonia, NH₃, is made by reacting nitrogen with hydrogen. Write the balanced equation for this reaction.

(2)

Oxygen, O₂, is also a simple molecular, covalent substance.

Draw a dot and cross diagram for the molecule of oxygen.

Figure 8 shows the arrangement of carbon atoms in diamond, graphene and a fullerene (C₆₀).

Figure 8

Consider these three substances.

Explain, in terms of their structures and bonding, their relative melting points, strengths and abilities to conduct electricity.

Which statement is not true about covalent bonding? 

What are the typical sizes, in orders of magnitude, of atoms and small molecules? 

Iodine and bromine are both halogens. The bonding in iodine is similar to the bonding in bromine.

Suggest two reasons why they bond in similar ways.

Complete the diagram below to show the bonding arrangement in a molecule of iodine.

Show the outer shell electrons only.

Explain why liquid iodine is unable to conduct electricity.

Iodine has an atomic number of 53 and xenon has an atomic number of 54. Explain why xenon exists as an atom where as iodine exists as a molecule.

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.