Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
What is a covalent bond?
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →Ethene (CH) is an organic molecule. Explain, using electron arrangement, how you can use a dot-and-cross diagram to confirm that each atom in ethene has a full outer shell.
Question 12
4 marks · Normal
Answer and see the solution →Table 1. Molecules and their covalent bonds Molecule Number of Covalent Bonds per Molecule H2 1 CH4 4 NH3 3 CO2 4 Using the data in Table 1, answer the following questions:
(a)[1 mark]Which molecule contains the greatest number of covalent bonds per molecule?
(b)[2 marks]Explain why CO has four covalent bonds per molecule.
(c)[1 mark]State how many covalent bonds exist in two molecules of ammonia (NH).
Question 13
1 mark · Normal
Answer and check →Which of the following dot-and-cross diagrams correctly represents the covalent bonding in a molecule of hydrogen chloride, HCl?
- A.A. H and Cl with one shared pair and Cl with 6 additional outer electrons.
- B.B. H and Cl with one shared pair and Cl with only 2 outer electrons.
- C.C. H and Cl with two shared pairs between them.
- D.D. H atom with two electrons, Cl atom with seven electrons, but none shared.
Question 14
2 marks · Normal
Answer and see the solution →Describe what happens to the electrons in the outer shells of two hydrogen atoms when they form a molecule of hydrogen, H.
Question 15
4 marks · Normal
Answer and see the solution →(a)[2 marks]Draw a dot-and-cross diagram to show the covalent bonding in an oxygen (O) molecule.
(b)[2 marks]Explain why there are two covalent bonds between the two oxygen atoms.
Question 16
3 marks · Normal
Answer and see the solution →A molecule of ammonia () is formed by nitrogen bonding covalently with three hydrogen atoms.
Given that each covalent bond is formed by the sharing of one pair of electrons, calculate the total number of electrons that nitrogen shares with hydrogen in ammonia.
Question 17
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 18
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 19
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.