11 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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Covalent Bonding (Edexcel GCSE Chemistry: Combined Science)
Exam Questions
50 mins12 questions2a3 marks
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)
| melting point in °C |
boiling point in °C |
ability to conduct electricity in liquid state |
|||
| ☐ | A | 1713 | 2950 | does not conduct | |
| ☐ | B | −78 | −33 | does not conduct | |
| ☐ | C | −39 | 357 | conducts | |
| ☐ | D | 801 | 1413 | conducts |
ii)
Ammonia, NH3, is made by reacting nitrogen with hydrogen.
Write the balanced equation for this reaction.
(2)
2b2 marks
Oxygen, O2, is also a simple molecular, covalent substance.
Draw a dot and cross diagram for the molecule of oxygen.
2c6 marks
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.
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31 mark
Which statement is not true about covalent bonding?
| ☐ | A | Two atoms share at least one pair of electrons between them | |
| ☐ | B | Covalent bonding can result in small molecules being formed | |
| ☐ | C | Covalent bonds are weaker than ionic bonds | |
| ☐ | D | Covalent bonding occurs to allow atoms to have stable, full outer shells of electrons |
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41 mark
What are the typical sizes, in orders of magnitude, of atoms and small molecules?
| Size of atoms and small molecules / m | |||
| ☐ | A | x 10-8 | |
| ☐ | B | x 10-9 | |
| ☐ | C | x 10-10 | |
| ☐ | D | x 10-11 |
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5a2 marks
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.
5b2 marks
Complete the diagram below to show the bonding arrangement in a molecule of iodine.
Show the outer shell electrons only.
5c2 marks
Explain why liquid iodine is unable to conduct electricity.
5d4 marks
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.
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