Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Covalent Bonding
68 practice questions
Topics covered
Practice questions
1–10 of 12 · Hard
Question 1
2 marks · Hard
Answer and see the solution →State what holds the atoms together in a covalent bond, and explain why a covalent bond only forms between certain atoms.
Question 2
5 marks · Hard
Answer and see the solution →Boron trifluoride (BF) is a covalent compound. Answer the following questions about its bonding.
(a)[1 mark]How many electrons are in the outer shell of a boron atom and of a fluorine atom?
(b)[2 marks]Draw a dot-and-cross diagram to show the covalent bonding in a molecule of BF. Use dots (•) for boron’s electrons and crosses (×) for fluorine’s electrons.
(c)[2 marks]Explain, using your diagram, why the central boron atom in BF does not have a full octet in its outer shell.
Question 3
2 marks · Hard
Answer and see the solution →Explain what a covalent bond is and describe how the sharing of electrons holds the bonded atoms together.
Question 4
2 marks · Hard
Answer and see the solution →Explain, using ideas about bonds and forces, why melting a substance with a simple molecular structure requires much less energy than melting a giant covalent structure such as diamond.
Question 5
5 marks · Hard
Answer and see the solution →The table shows data for three simple molecular substances:
Substance Relative molecular mass (Mr) Melting point (°C) Boiling point (°C) Electrical conductivity A 32 -210 -183 does not conduct B 44 -56 -1 does not conduct C 160 -7 59 does not conduct (a)[2 marks]Describe the trend shown by the melting points and boiling points as the relative molecular mass increases.
(b)[2 marks]Substance C is liquid at room temperature (25°C). Explain why substance C is a liquid at this temperature but substance A is a gas.
(c)[1 mark]Explain why none of these substances conduct electricity in any state.
Question 6
2 marks · Hard
Answer and see the solution →State one property that distinguishes a simple molecular structure from a giant covalent structure. Explain how this property relates to the forces present in each structure.
Question 7
2 marks · Hard
Answer and see the solution →Diamond is used for industrial cutting tools, while graphite is used as a lubricant. Explain, in terms of structure and bonding, why graphite can be used as a lubricant but diamond cannot.
Question 8
5 marks · Hard
Answer and see the solution →The three allotropes of carbon—diamond, graphite, and C60 fullerene—have different abilities to conduct electricity.
(a)[1 mark]State which, if any, of these allotropes can conduct electricity.
(b)[4 marks]For each allotrope, explain your answer by referring to their bonding and the movement of electrons.
Question 9
2 marks · Hard
Answer and see the solution →Describe the structure and bonding in C60 fullerene, referring to how carbon atoms are arranged and bonded in this allotrope.
Question 10
8 marks · Hard
Answer and see the solution →This question is about the differences in properties between substances with simple molecular structures and those with giant covalent structures.
(a)[2 marks]Explain why substances with simple molecular structures, such as chlorine (Cl₂), have low melting and boiling points.
(b)[3 marks]Diamond and graphite are both forms of carbon, but diamond is much harder than graphite. Explain, in terms of structure and bonding, why diamond is harder than graphite.
(c)[3 marks]State and explain whether Cl₂ can conduct electricity. Then compare this with the ability of diamond to conduct electricity, explaining your reasoning.