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CIE iGCSE Co-Ordinated Science C8.3 Group VII properties Exam Style Questions Paper 4

CIE iGCSE Co-Ordinated Science Paper 4 - All Chapters

Question

Table 5.1 gives some information about the Group VII elements.
(a) (i) Complete Table 5.1 to show the colour of bromine.
(ii) Complete Table 5.1 to show the state of chlorine at room temperature.
(iii) Complete Table 5.1 to predict the melting point of fluorine. Use ideas about trends down a group to help you.
(b) Fig. 5.1 shows a diagram of a sodium atom.
(i) Sodium is in Period 3 of the Periodic Table.
Use Fig. 5.1 to explain why sodium is in Period 3.
(ii) A sodium atom is neutral. Explain why.
Use ideas about the particles in an atom.
(c) Chlorine reacts with sodium to form the compound sodium chloride.
Sodium has the electronic structure 2.8.1.
Chlorine has the electronic structure 2.8.7.
Draw a dot-and-cross diagram to show the ions in sodium chloride.
Show outer-shell electrons only. Include the charges on the ions.
(d) Solid sodium chloride has a lattice structure.
Put a tick (✓) next to the statement that describes this lattice structure.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic C8.3 — Group VII properties (Part (a))
• Topic C2.2 — Atomic structure and the Periodic Table (Part (b))
• Topic C2.4 — Ions and ionic bonds (Part (c))
• Topic C2.4 — Ions and ionic bonds (Part (d))

▶️ Answer/Explanation

(a)(i) red-brown

Bromine is a red-brown liquid at room temperature.

(a)(ii) gas

Chlorine has a boiling point of \(-35\,^{\circ}\text{C}\), below room temperature.
This means chlorine exists as a gas at room temperature.

(a)(iii) in the range \(-189\) to \(-272\,^{\circ}\text{C}\)

Melting and boiling points decrease going up Group VII.
Since chlorine melts at \(-101\,^{\circ}\text{C}\), fluorine (above chlorine) must melt at a lower temperature than this.

(b)(i) sodium has three occupied electron shells

Fig. 5.1 shows the sodium atom has three electron shells in use.
The period number corresponds to the number of occupied electron shells, so sodium is in Period 3.

(b)(ii) protons are positive and electrons are negative; equal numbers of each

A sodium atom contains protons, which carry a positive charge, and electrons, which carry a negative charge.
Since the number of protons equals the number of electrons, the charges cancel out and the atom is neutral.

(c) 

Sodium loses one electron to form Na\(^{+}\), leaving a full outer shell from the shell below.
This electron is transferred to chlorine, giving Cl\(^{-}\) a full outer shell of 8 electrons.

(d) regular arrangement of alternating positive and negative ions

Solid sodium chloride forms a giant ionic lattice.
The positive sodium ions and negative chloride ions are arranged in a regular, alternating pattern.

Question

Table 5.1 gives some information about the properties of the Group VII elements.
(a)(i) Predict the boiling point of chlorine. Write your answer in Table 5.1.
(ii) Predict the state at room temperature of bromine. Write your answer in Table 5.1.
(b) Bromine has a lower boiling point than iodine. Tick (✓) one box to show the correct explanation.
(c) Chlorine, \(\text{Cl}_2\), reacts with sodium bromide, NaBr, to form sodium chloride, NaCl, and bromine.
(i) Construct the balanced symbol equation for this reaction.
(ii) Sodium chloride is an ionic compound.
A sodium atom has electronic structure 2.8.1, and a chlorine atom has electronic structure 2.8.7.
Draw a dot-and-cross diagram to show the ions formed when sodium bonds with chlorine, including the charges on the ions.
(iii) Concentrated aqueous sodium chloride conducts electricity. Tick (✓) one box to show the correct explanation.
(iv) State the name of the product at the anode in the electrolysis of concentrated aqueous sodium chloride.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic C8.3 — Group VII properties (Parts (a)(i), (a)(ii), and (b))
• Topic C6.2 — Rate of reactions (Part (c)(i))
• Topic C2.4 — Ions and ionic bonds (Part (c)(ii) — dot-and-cross diagram)
• Topic C4.1 — Electrolysis (Parts (c)(iii) and (c)(iv))

▶️ Answer/Explanation

(a)(i) Between −122 °C and −30 °C

Chlorine’s boiling point lies between fluorine’s (−188 °C) and bromine’s (59 °C), following the increasing trend down the group.
Any value in this inclusive range is accepted.

(a)(ii) Liquid

Bromine’s boiling point (59 °C) is above room temperature but its melting point is below it, so bromine exists as a liquid at room temperature.

(b) The forces between bromine molecules are weaker

Halogens are simple molecular substances held together by weak intermolecular forces.
These forces increase down the group as molecules get larger, so bromine (smaller molecule) has weaker forces than iodine, giving it a lower boiling point.

(c)(i) \( \text{Cl}_2 + 2\text{NaBr} \rightarrow 2\text{NaCl} + \text{Br}_2 \)

Chlorine displaces bromine from sodium bromide because chlorine is more reactive (higher up Group VII).
The equation must be balanced for both atoms and formula units.

(c)(ii) 

Sodium (2.8.1) loses one electron to form Na\(^+\) with structure 2.8.
Chlorine (2.8.7) gains that electron to form Cl\(^-\) with structure 2.8.8.
The diagram should show the transferred electron as a cross on the chloride ion, with correct + and − charges shown outside square brackets.

(c)(iii) Contains ions which can move

Concentrated aqueous sodium chloride conducts electricity because it contains mobile ions (Na\(^+\) and Cl\(^-\)) that can carry charge through the solution.

(c)(iv) Chlorine

At the anode (positive electrode), chloride ions lose electrons (oxidation) to form chlorine gas.

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