AQA GCSE Chemistry (8462), Higher tier · Bonding, structure and the properties of matter › Chemical bonds: ionic, covalent and metallic
Practise Covalent bonding. 19 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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How many covalent bonds are there in one molecule of methane, CH4?
4
Give the total number of non-bonding pairs of electrons (lone pairs) in one molecule of carbonyl chloride.
8
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Covalent bonds form between non-metal atoms.
(a) What is a covalent bond? Tick (✓) one box.[1]
A shared pair of electrons between two atoms
The attraction between oppositely charged ions
The attraction between positive ions and delocalised electrons
A weak force between molecules
(b) Which substance consists of small molecules? Tick (✓) one box.[1]
Ammonia
Diamond
Poly(ethene)
Sodium chloride
(c) How many covalent bonds are there in one molecule of methane, CH4?[1]
(d) Silicon dioxide contains covalent bonds. What type of structure does silicon dioxide have? Tick (✓) one box.[1]
Giant covalent
Giant ionic
Giant metallic
Small molecules
Show the answer and mark scheme
(a)Answer: A shared pair of electrons between two atoms
(b)Answer: Ammonia
(c)Answer: 4
4
(d)Answer: Giant covalent
Question 2Medium5 marks
Dot and cross diagrams show how the outer electrons are arranged in molecules.
(a) How many pairs of electrons are shared in a molecule of ammonia, NH3?[1]
(b) How many non-bonding pairs of electrons are there on the oxygen atom in a molecule of water, H2O?[1]
(c) Explain why a hydrogen atom forms only one covalent bond.[1]
(d) Describe the dot and cross diagram for a molecule of hydrogen chloride, HCl.[2]
Show the answer and mark scheme
(a)Answer: 3
3
(b)Answer: 2
2
(c)Answer: It has only one electron; sharing one pair gives it a full first shell (2 electrons).
hydrogen has one electron / its (first) shell is full with 2 electrons after sharing one pair
(d)Answer: One pair of electrons is shared between H and Cl (one electron from each); the chlorine atom also has three non-bonding pairs.
one pair of electrons shared between H and Cl (one electron from each atom)
the chlorine atom has three non-bonding pairs / 8 electrons in its outer shell
Question 3Hard6 marks
A molecule of methane, CH4, can be represented by a dot and cross diagram or by a ball and stick model.
(a) Give one advantage and one limitation of each of these two representations of methane.[4]
(b) A molecule contains one carbon atom, two hydrogen atoms and two chlorine atoms. Each chlorine atom forms one covalent bond. Give the molecular formula of the molecule and the total number of covalent bonds in the molecule.[2]
Show the answer and mark scheme
(a)Answer: Dot and cross: shows which atom each bonding electron came from, but not the 3D shape. Ball and stick: shows the 3D shape, but not the electrons (bonds are shown as sticks).
dot and cross: advantage — shows which atom the bonding electrons came from / shows the shared pairs of electrons
dot and cross: limitation — does not show the 3D shape / bond angles / the relative sizes of the atoms
ball and stick: advantage — shows the 3D shape / arrangement of the atoms in space / bond angles
ball and stick: limitation — bonds are shown as sticks (a bond is a shared pair of electrons) / atoms are not to scale / electrons are not shown