IGCSE Co-ordinated Sciences (Double Award) 0654 · Chemistry · 16

0654.C2.4.01 — Describe the formation of positive ions, known as cations, and negative ions, known as anions: past paper questions

5 real questionsasked in 3 of the last 10 exam series2025–2025usually: Draw, State, Explain

Real questions on 0654.c2.4.01 — describe the formation of positive ions, known as cations, and negative ions, known as anions

The newest 5 of 5 written questions. Open one to see it on the real paper.

0654/32 · October/November 2025 · Q8a(i)[2]
Fig. 8.1 shows the formation of a sodium ion from a sodium atom. Na Na sodium atom sodium ion + Fig. 8.1 Cl Cl chlorine atom chloride ion Complete Fig. 8.2 to show the formation of a chloride ion from a chlorine atom.
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0654/41 · October/November 2025 · Q5c[3]
Fig. 5.1 shows the electronic structures of a sodium atom and an oxygen atom. Na O Fig. 5.1 (c) The Group I element sodium reacts with oxygen to make sodium oxide, Na 2 O. Draw the electronic structures of the sodium ion and oxide ion in sodium oxide. Include the charges on the ions.
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0654/33 · May/June 2025 · Q5b(iv)[2]
Sodium chloride is also made by reacting an acid with an alkali. State the acid and the alkali that is used. acid
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0654/33 · May/June 2025 · Q5b(v)[1]
Chlorine is a halogen. The halogens are found in Group VII of the Periodic Table and have similar chemical properties. Explain why the halogens have similar chemical properties.
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0654/42 · February/March 2025 · Q5b[2]
An aluminium atom, Al, forms an aluminium ion, Al 3+ . Describe, in terms of electrons, how an aluminium ion is formed.
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What examiners said

The majority of candidates incorrectly wrote two of sodium, chloride and hydrogen. Some were able to identify hydrochloric acid but it was very rare to see sodium hydroxide as the alkali.
— Examiner report, May/June 2025, 0654/33 Q5(b)(iv) (Cambridge)

Candidates generally gave specific properties, for example, they are all gases, or repeated the information in the question about them being in the same group. Others said it was because they all end in ‘ine’ or gave more vague answers about having the same outer shell with no reference to the number of electrons. Candidates are encouraged to carefully read the question and ensure that their respo...
— Examiner report, May/June 2025, 0654/33 Q5(b)(v) (Cambridge)

A small number of candidates described electrons as being shared rather than being lost. Most candidates that recognised electrons were lost also stated that three electrons were lost.
— Examiner report, February/March 2025, 0654/42 Q5(b) (Cambridge)

Practise this topic

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Practise 0654.c2.4.01 — describe the formation of positive ions, known as cations, and negative ions, known as anions

In the syllabus

16 0654.C2.4.01 — Describe the formation of positive ions, known as cations, and negative ions, known as anions

Describe the formation of positive ions, known as cations, and negative ions, known as anions
State that an ionic bond is a strong electrostatic attraction between oppositely charged ions
Describe the formation of ionic bonds 5 Describe the formation of ionic bonds between elements from Group I and between ions of metallic and non-metallic Group VII, including the use of dot-and-cross elements, including the use of dot-and-cross diagrams diagrams
Describe the properties of ionic compounds: 6 Explain in terms of structure and bonding the (a). high melting points and boiling points properties of ionic compounds: (b). good electrical conductivity when (a). high melting points and boiling points aqueous or molten and poor when solid (b). good electrical conductivity when (c). generally soluble in water aqueous or molten and poor when solid
Describe the giant lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions, exemplified by sodium chloride

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