Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want group properties — alkali metals, halogens and noble gases — to become reliable marks instead of isolated facts about each element.
What query it owns: how to understand and revise group properties in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the group-properties revision-guide angle, while Tutopiya’s Group Properties subtopic page owns the learning resource and the free Group Properties quiz owns the practice.

Elements in the same group share similar chemical properties because they have the same number of electrons in their outer shell. Cambridge IGCSE Coordinated Science (0654) tests Group 1 (alkali metals), Group 7 (halogens) and Group 0 (noble gases) — their reactions, trends and displacement reactions. This guide links each group’s behaviour to electron arrangement so you can answer describe, explain and predict questions with confidence.

Key takeaways

• Group 1 (alkali metals): one outer electron; form +1 ions; react with water to give hydrogen and an alkali; reactivity increases down the group.
• Group 7 (halogens): seven outer electrons; form −1 ions; exist as diatomic molecules (F₂, Cl₂, Br₂, I₂); reactivity decreases down the group.
• Group 0 (noble gases): full outer shell; unreactive; exist as monatomic gases.
• A more reactive halogen displaces a less reactive halogen from its salt solution.
• Group trends follow from atomic size, shielding and ease of losing/gaining outer electrons.

What are group properties in Cambridge IGCSE Coordinated Science?

Group properties are the shared chemical behaviours of elements in the same vertical column of the periodic table. Because outer-shell electron numbers match, elements in a group form similar ions and show predictable trends in reactivity. Examiners frequently test reactions of sodium and potassium with water, halogen displacement, and why noble gases are inert.

You can read the full explanation, diagrams and notes on Tutopiya’s Group Properties subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Group 1 reactivity	Loses one outer electron easily	”Describe the reaction of potassium with water.”
Group 7 displacement	More reactive halogen displaces less reactive	”Explain why chlorine displaces bromine from KBr.”
Diatomic halogens	Halogens exist as X₂ molecules	”State the formula of chlorine at room temperature.”
Noble gas stability	Full outer shell = unreactive	”Explain why helium is unreactive.”
Trend down a group	Atomic size and shielding increase	”Explain why caesium is more reactive than lithium.”

Group 1 — alkali metals

Property / reaction	Detail
Outer electrons	1
Ion formed	M⁺ (e.g. Na⁺, K⁺)
Reaction with water	Metal + water → metal hydroxide + hydrogen
Observations (Na)	Floats, melts to ball, moves, fizzes, hydrogen ignites
Reactivity trend	Increases down the group (Li < Na < K < Rb < Cs)
Stored under	Oil (react with air and water)

Group 7 — halogens

Halogen	State at room temp	Colour	Reactivity
Fluorine (F₂)	Gas	Pale yellow	Most reactive
Chlorine (Cl₂)	Gas	Green-yellow
Bromine (Br₂)	Liquid	Red-brown
Iodine (I₂)	Solid	Grey-black (purple vapour)	Least reactive

Displacement rule: chlorine + potassium bromide → potassium chloride + bromine (chlorine is more reactive and displaces bromine).

Group properties in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical group properties stem
Describe	Observations of a reaction	”Describe what you see when sodium reacts with water.”
Explain	Link to electron structure	”Explain why reactivity increases down Group 1.”
Write a word/symbol equation	Balanced reaction	”Write the equation for lithium with water.”
Predict	Apply displacement or trend	”Predict whether iodine displaces chlorine from NaCl.”
State	Short factual answer	”State the ion formed by a Group 1 metal.”

Worked exam-style stems (how to answer the wording)

1. “Describe the reaction of sodium with water.” Sodium floats, melts into a ball, moves across the surface, fizzes vigorously and may ignite the hydrogen produced; an alkaline solution forms. Mark-scheme reward: fizzing + hydrogen + alkaline solution + movement/floating.
2. “Chlorine is bubbled into potassium iodide solution. Describe what happens.” Solution turns brown; iodine is displaced because chlorine is more reactive than iodine. Reward: brown colour + iodine displaced + chlorine more reactive.
3. “Explain why the noble gases are unreactive.” They have a full outer electron shell, so they do not easily gain or lose electrons. Reward: full outer shell + no tendency to gain/lose electrons.

Practise on the Group Properties quiz.

How group properties connect to the rest of Coordinated Science chemistry

Group properties follow Periodic Trends and link to Noble Gases and the Reactivity Series. The Cambridge IGCSE Coordinated Science resource hub links every Chemistry subtopic.

Common mistakes students make

• Writing halogens as single atoms (Cl) instead of diatomic molecules (Cl₂).
• Predicting iodine will displace chlorine (it will not — iodine is less reactive).
• Forgetting alkali metals produce hydrogen and an alkaline solution with water.
• Stating Group 7 reactivity increases down the group (it decreases).
• Confusing Group 0 (noble gases) with Group 7 (halogens).

When you need more support

If group-properties questions keep costing marks, work through the Group Properties quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

What are alkali metals? Group 1 metals (Li, Na, K, Rb, Cs) that react with water to form alkalis (metal hydroxides) and hydrogen.

Why do halogen displacement reactions occur? A more reactive halogen takes the place of a less reactive halogen in a compound because it gains electrons more easily.

Why are noble gases unreactive? They have a complete outer electron shell and do not need to gain or lose electrons to achieve stability.

How do I revise group properties effectively? Learn Group 1 reactions with water, halogen states and colours, displacement rules, then take the Group Properties quiz.

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