Edexcel IGCSE Chemistry

Topic Questions

IGCSEChemistryEdexcelTopic Questions1. Principles of Chemistry1.7 Covalent Bonding

1.7 Covalent Bonding

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11 mark

The diagram shows the structures of three substances that have giant covalent structures.

1-7-q4-edexcel-igcse-chemistry 

Which does not provide the correct explanation of the property of a substance?

  Substance Property Explanation
A graphite conducts electricity its ions are free to move through the layers
B diamond hard each carbon atom is covalently bonded to four other carbon atoms
C silicon dioxide high melting point it has many strong covalent bonds which require a large amount of energy to break
D graphite soft its layers can slide over each other

  ☐ A  
  ☐ B  
  ☐ C  
  ☐ D  

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2a1 mark

Which best describes a covalent bond?

  ☐ A Sea of delocalised electrons and positive metal ions
  ☐ B Attraction between positive and negative ions
  ☐ C Shared pair of electrons between two non-metal atoms
  ☐ D Weak intermolecular forces 

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2b1 mark

Which of the following substances will bond covalently?

  ☐ A Sodium oxide
  ☐ B Sodium
  ☐ C Sodium bromide
  ☐ D Oxygen

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2c1 mark

Hydrogen is an atom which has one electron in the outermost shell. Complete the dot-and-cross diagram to show the bonding in a hydrogen molecule.

1-7-2c-e-hydrogen-incomplete-dot-cross-a

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2d1 mark

Hydrogen is a gas at room temperature.

Why is hydrogen a gas at room temperature?

Tick ( ) one box

The intermolecular forces are strong  
The bonding in hydrogen is weak   
The intermolecular forces are weak   

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3a4 marks

This question is about allotropes of carbon. 

Match the name of the substance to its structure. 

You must only draw one line from each substance. 

covalent-match-up-

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3b1 mark

What type of bonding is found in the structures in part (a)?

Tick () one box. 

 Ionic   Covalent   Metallic  

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3c1 mark

Which substance cannot conduct electricity?

Tick () one box.

 Diamond  
 C60 fullerene   
 Graphite  
 

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3d2 marks

Complete the sentence to describe and explain the melting points of diamond and graphite. 

Their melting points are ____________________ due to strong covalent bonds needing lots of ___________________ to break. 

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4a2 marks

Hydrogen and carbon atoms form the hydrocarbon molecule methane. 

The diagram in Figure 1 shows how the outer electrons are arranged in an atom of hydrogen and carbon.  

1-4-covalent-bonding-2a-a

Figure 1

Complete Figure 2 to show how the outer electrons are arranged in a molecule of methane (CH4). 

1-4-covalent-bonding-2a-b

Figure 2

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4b1 mark
What is the type of bond in a molecule in methane? 


Tick () one box. 

Metallic  
Ionic   
Covalent   

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4c3 marks

Methane has a boiling point of -162 °C. At room temperature it is a gas.

Explain why methane is a gas at room temperature.

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4d1 mark

Methane is a simple molecule and it does not conduct electricity. 

Which statement is the correct reason for this? 

Tick () one box. 

Electrons are fixed in position  
The ions are free to move and carry a charge   
There are no free electrons to carry the charge   
The bonds contain no electrons   

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5a1 mark

The alkanes are a family of hydrocarbons with the general formula CnH2n+2. Ethane, C2H6, and butane, C4H10, are examples of alkanes. 

Ethane has a boiling point of -89 °C and butane has a higher boiling point of -1 °C.

Why is the boiling point of butane higher than ethane?

  ☐ A Butane is ionically bonded
  ☐ B Butane has a higher Mr than ethane 
  ☐ C Butane has stronger bonds between the carbon and hydrogen atoms
  ☐ D Ethane has a higher Mr than butane

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5b3 marks

Complete the sentences below using words from the box.

conduct               atoms              free                 shells

fixed                      insulate                     ions                    electrons


Ethane and butane do not ________________ electricity because there are no ________________ ions / _______________ that are able to move and carry charge. 

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5c1 mark

What is the type of bonding in ethane and butane?

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5d1 mark

Ethane and butane only contains single bonds. Double bonds can also form between a different family of hydrocarbons called alkenes. 

Which of the following statements is correct?

Tick () one box. 

A double bond contains two electrons  
A double bond contains two pairs of electrons   

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1a4 marks

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)
 
blank-diatomic-dot-and-cross
 
ii)
Describe the forces of attraction in a covalent bond.
 
(2)

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1b5 marks

The diagram shows three different structures of carbon.

 
diamond graphite fullerene
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)

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2a2 marks

This question is about some compounds of the elements in Group 4 of the Periodic Table.

When carbon dioxide dissolves in water, a weak acid forms.

i)
Which of these could be the pH of this weak acid?

(1)

  ☐ A 1
  ☐ B 5
  ☐ C 7
  ☐ D 9

ii)
Which of these is a correct statement about acids?
(1)
  ☐ A acids contain OH− ions
  ☐ B acids are electron donors
  ☐ C acids are proton acceptors
  ☐ D acids are proton donors

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2b2 marks

When lead(II) carbonate is heated, lead(II) oxide and carbon dioxide form.

i)
Give the name of this type of reaction.
(1)
ii)
Complete the equation for this reaction.
(1)

PbCO3 → .............................................. + ..............................................

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2c7 marks

Silicon dioxide, SiO2, and silicon(IV) chloride, SiCl4, are both covalently bonded compounds. The table shows the melting and  boiling points of these two compounds, and the physical state of silicon dioxide at room temperature.

Compound Melting point in °C Boiling point in °C Physical state at
room temperature
SiO2 1710 2230 solid
SiCl4 −69 58  

i)
Complete the table by giving the physical state of silicon(IV) chloride at room temperature.

(1)

ii)
Explain, in terms of structure and bonding, why silicon dioxide has a much higher melting point than silicon(IV) chloride.

(6)

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3a1 mark

This question is about covalent bonding.

What is a covalent bond? 

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3b1 mark

Complete the dot and cross diagram in to show the bonding in propane. 

aqa-gcse-2-1h-tq-3b-propane-dot-and-cross-diagram
(1) 

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3c2 marks

Explain why propane cannot conduct electricity. 

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3d2 marks

Carbon dioxide, CO2, bonds in a similar way to propane. Complete the diagram to show the bonding.

1-4-covalent-bonding-1d

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4a2 marks

This question is about the bonding and structure of diamond.

State two uses of diamonds.

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4b3 marks

The diagram shows the outer electron shells of carbon atoms in a lattice structure of diamond.

Using dots, add electrons to the diagram to represent the bonding arrangement.

aqa-gcse-2-3h-tq1b-diamond-dot-and-cross-diagram

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4c4 marks

Explain why diamond has a high melting point. 

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4d2 marks

The type of bonding in ethene gas, C2H4, is the same type of bonding that occurs in diamond. Explain why ethene is a gas at room temperature.

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4e4 marks

The boiling point of other molecules in the same family as ethene are shown below.

Molecule Boiling point / °C
Ethene -104
Propene -48
Butene -6
Pentene  30



State and explain the trend in the boiling point. 

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5a2 marks

This question is about the properties and bonding in allotropes of carbon. 

Substance X is an allotrope of carbon and has the following properties and uses:

  • It is strong
  • It is a good conductor or electricity
  • It is used to overlay monitor screens to make them touchscreen

Identify substance X.

Explain your answer.

          

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5b2 marks

Buckminsterfullerene is another allotrope of carbon.

Explain why this substance can be used as a lubricant. 

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5c3 marks

Fullerenes are also used as catalysts and in electronics.

Suggest why they can each be used for these applications.

   

catalysts: ____________________________________________ 

   electronics: ___________________________________________

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5d2 marks

Explain how a catalyst increases the rate of a reaction. 

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1a
Sme Calculator2 marks

Halon 1301 is a compound used in some fire extinguishers.

Halon 1301 has the percentage composition by mass of

C 8.05%   Br 53.69%   F 38.26%

Show, by calculation, that the empirical formula of this compound is CBrF3 

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1b2 marks

The diagram shows the displayed formula of a molecule of Halon 1301.

 
cbrf3-halon-1301
 

Draw a dot-and-cross diagram to show all the outer electrons in this molecule.

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1c2 marks

The boiling point of Halon 1301 is —58°C.

 

Explain why Halon 1301 has a low boiling point.

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2a2 marks

Diamond, graphite and silicon dioxide all have giant covalent structures.

The diagram shows the structures of these three substances.

covalent-structures-edexcel-2019ju1c

Explain why silicon dioxide has a high melting point.

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2b2 marks

Explain why graphite conducts electricity. 

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2c2 marks

State why diamond is hard but graphite is soft.

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3a3 marks

Carbon dioxide changes directly from a solid to a gas without becoming a liquid.

i)
Give the name of the change of state from solid to gas.

(1)

ii)
Describe the test for carbon dioxide gas.

(2)

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3b2 marks

Carbon dioxide is a simple molecular covalent substance.

Explain why carbon dioxide turns from a solid to a gas at a very low temperature.

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3c6 marks

Diamond and graphite are both giant covalent substances made up of carbon atoms.

  • diamonds are used in cutting tools
  • graphite is used in pencils to make marks on paper

Explain, with reference to structure and bonding, why each substance is suitable for its particular use.

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4a3 marks

Chlorine, bromine and iodine are elements in the Periodic Table.

Explain how the position of these elements in the Periodic Table depends on their electronic configurations.

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4b8 marks

Chlorine reacts with methane to form CH3Cl and HCl

 
i)
State the condition necessary for this reaction.
 
(1)
 
ii)
Give the equation for this reaction.
 
(1)
 
iii)
The bonds in a molecule of CH3Cl are covalent.
 
Explain, in terms of electrostatic attractions, what is meant by a covalent bond.
 
(2)
 
iv)
Draw a dot‐and‐cross diagram for a molecule of CH3Cl
 
Show only the outer electrons of the atoms.
 
(2)
 
chloromethane-dot-and-cross-blank
 
v)
CH3Cl has a simple molecular structure.
 
Explain why CH3Cl has a low boiling point.
 
(2)

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4c2 marks
Graphite is another substance that contains covalent bonds.
 

The diagram shows the structure of graphite.

 
graphite-edxcel-2020nov1c
 

Most covalent substances do not conduct electricity. 

Explain why graphite is able to conduct electricity.

 
(2)

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51 mark

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 co2-bonding-option-a
  ☐ B co2-bonding-option-b
  ☐ C co2-bonding-option-c
  ☐ D co2-bonding-option-d

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6a3 marks

Diamond is a naturally‐occurring form of carbon.

It has a giant molecular structure.

Explain, with reference to its structure and bonding, why diamond has a high melting point.

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6b3 marks

C60 fullerene is another form of carbon.

The diagram shows a molecule of C60 fullerene.

2019-ju1cr-q9b

i)
Explain why C60 fullerene has a much lower melting point than diamond.

(2)

ii)
C60 fullerene is used by doctors when injecting medicines into their patients.

C60 fullerene allows medicines, which might damage some parts of the body, to reach the part of the body where they are needed.

Suggest why C60 fullerene is suitable for this purpose.

(1)

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6c5 marks

Graphite is another naturally‐occurring form of carbon.
Graphite can be used in pencils because it is soft and can leave marks on paper.
Graphite can also be used as a conductor of electricity.

Explain why graphite is soft and conducts electricity.
Refer to structure and bonding in your answer.

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7a4 marks

This question is about carbon and its compounds.

i)
Draw a dot-and-cross diagram to show the outer shell electrons in a molecule of carbon dioxide, CO2.
 

(2)

ii)
The atoms in carbon dioxide are held together by covalent bonds.
Describe the forces of attraction in a covalent bond.

(2)

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7b7 marks

The diagram shows three different structures of carbon.

 
allotropes-of-carbon
i)
Explain why graphite conducts electricity.

(2)

ii)
Explain why diamond has a much higher melting point than C60 fullerene.
Refer to structure and bonding in your answer.

(5)

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81 mark

Silicon dioxide, SiO2, and silicon(IV) chloride, SiCl4, are both covalently bonded compounds.

The table below shows the melting point and boiling point of these compounds.

Compound Melting point / o C Boiling point / o C
Silicon dioxide 1710 2230
Silicon(IV) chloride -69 58

Which statement is not correct about the two compounds?

  ☐ A at room temperature silicon dioxide is a solid and silicon(IV) chloride is a liquid
  ☐ B silicon dioxide has a giant covalent structure
  ☐ C silicon(IV) chloride has a lower melting point as it has fewer covalent bonds to overcome
  ☐ D silicon(IV) chloride has a simple molecular structure

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91 mark

Ammonia, NH3, is a small covalent molecule.

How many non-bonding, outer-shell electrons are present in one molecule of ammonia?

  ☐ A 0
  ☐ B 2
  ☐ C 5
  ☐ D 6

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