CIE iGCSE Co-Ordinated Science C8.3 Group VII properties Exam Style Questions Paper 3
Question
Most-appropriate topic codes (Cambridge IGCSE Coordinated Sciences 0654):
• Topic C2.4 — Ions and ionic bonds (Part (a)(i))
• Topic C2.4 — Ions and ionic bonds (Part (a)(ii))
• Topic C8.3 — Group VII properties (Part (b))
• Topic C7.1 — Characteristic properties of acids and bases (Part (c))
▶️ Answer/Explanation
(a)(i) eight electrons added to outer shell; – sign shown
A chlorine atom has 7 electrons in its outer shell. It gains one electron to achieve a stable octet, becoming a chloride ion (Cl⁻) with a single negative charge.
(a)(ii) generally soluble in water; good electrical conductivity; high melting point
Ionic compounds have high melting points due to strong electrostatic attractions. They conduct electricity when dissolved in water (but not when solid) because ions are free to move. They are generally soluble in water.
(b) (pale) yellow-green; gas
Chlorine is a pale yellow-green gas at room temperature and pressure. It is a diatomic molecule (Cl₂) with a distinctive colour.
(c) hydrochloric acid; sodium hydroxide
Neutralisation of hydrochloric acid with sodium hydroxide produces sodium chloride and water. The acid provides chloride ions, and the alkali provides sodium ions.
Question
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic C2.2 — Atomic structure and the Periodic Table (Part (a))
• Topic C8.1 — Arrangement of elements (Part (b)(i) & (b)(ii))
• Topic C8.2 — Group I properties (Part (b)(iii) & (b)(v))
• Topic C8.3 — Group VII properties (Part (b)(vi))
• Topic C8.5 — Noble gases (Part (b)(iv))
▶️ Answer/Explanation
(a)
The elements are listed in order of their proton / atomic number.
Moving from left to right across the Periodic Table, the elements become less metallic.
These metals form coloured compounds and are known as the transition elements.
As you move across a period, the increasing number of outer-shell electrons makes it progressively harder for atoms to lose electrons and behave as metals. Transition elements sit in the central block of the Periodic Table and are characterised by variable oxidation states, catalytic behaviour, and the formation of coloured ions and compounds.
(b)(i)
S, T, or V
S represents hydrogen (Group I, Period 1), which exists as the diatomic molecule $\text{H}_2$ at room temperature. T and V are halogens (Group VII) which also exist as diatomic molecules — fluorine ($\text{F}_2$) and chlorine ($\text{Cl}_2$) respectively — and are gases at room temperature. Any one of these three letters is a correct answer.
(b)(ii)
P, Q, or R
P, Q, and R are all metals located in Group I (alkali metals), and metals are solids at room temperature. They represent lithium, sodium, and potassium respectively, all of which have melting points well above room temperature. Any one of these three letters is a correct answer.
(b)(iii)
P, Q, or R
Alkali metals occupy Group I of the Periodic Table, excluding hydrogen (S, Period 1) which is a non-metal. P (lithium, Period 2), Q (sodium, Period 3), and R (potassium, Period 4) are all alkali metals with one outer-shell electron, making them highly reactive. Any one of these three letters is a correct answer.
(b)(iv)
X, Y, or Z
Noble gases are found in Group VIII (Group 0) of the Periodic Table and have a completely full outer electron shell. X represents helium (Period 1), Y represents neon (Period 2), and Z represents argon (Period 3) — all of which are monatomic, colourless, and extremely unreactive gases at room temperature. Any one of these three letters is a correct answer.
(b)(v)
R
Reactivity of alkali metals increases down Group I as the outer electron is further from the nucleus and more easily lost. Among the Group I metals shown, R sits lowest in the group (Period 4 — potassium) and is therefore the most reactive metal in Fig. 5.1.
(b)(vi)
T
Reactivity of halogens decreases down Group VII as each successive element has a greater atomic radius, making it harder to attract an additional electron. T sits higher in the group (Period 2 — fluorine) than V (Period 3 — chlorine), making T the most reactive halogen shown in Fig. 5.1.