11 mark
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?
| ☐ | A | 2 | |
| ☐ | B | 3 | |
| ☐ | C | 4 | |
| ☐ | D | 6 |
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Covalent Bonding (Edexcel GCSE Chemistry: Combined Science)
Exam Questions
50 mins12 questions21 mark
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?
| hydrogen | carbon | oxygen | chlorine | |||
| ☐ | A | 1 | 4 | 6 | 7 | |
| ☐ | B | 1 | 4 | 2 | 1 | |
| ☐ | C | 1 | 4 | 4 | 2 | |
| ☐ | D | 1 | 2 | 6 | 2 |
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3a3 marks
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.
3b3 marks
Ethanol has a boiling point of 79 °C. Explain why ethanol has a low boiling point.
3c2 marks
Explain, in terms of particles, why ethanol does not conduct electricity.
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41 mark
Methane and water are both simple molecules containing covalent bonds.
Which statement is not correct?
| ☐ | A | weak intermolecular forces of attraction exist between molecules | |
| ☐ | B | a covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the atoms involved | |
| ☐ | C | methane and water do not conduct electricity as they have no free electrons | |
| ☐ | D | there is a strong electrostatic attraction within the molecule between oppositely charged ions |
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5a4 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)
ii)
Describe the forces of attraction in a covalent bond.
(2)
5b5 marks
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)
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61 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 |  |
|
| ☐ | B |  |
|
| ☐ | C |  |
|
| ☐ | D |  |
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7a2 marks
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.
7b1 mark
Which of the following set of properties is most likely to be hydrogen sulfide?
| Boiling point in °C | Does it conduct electricity in the liquid state? | ||
| ☐ | A | 2230 | No |
| ☐ | B | 100 | No |
| ☐ | C | -60 | No |
| ☐ | D | 2750 | Yes |
7c2 marks
The atoms in carbon dioxide are held together by covalent bonds.
Describe the forces of attraction in a covalent bond.
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