Group Properties & Trends

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Group Properties & Trends (Chemistry, CIE) — use them in your lesson, or run the topic as a live class game.

Notes

Group I (Alkali Metals) – Physical Properties

Group I metals are called **alkali metals** because they form alkaline solutions with water.
They are **soft** and can be cut with a knife; softness increases down the group.
Freshly cut surfaces are **shiny and silvery**.
They have **low melting points** (some melt on a hot day) and **low densities** compared to other metals.
Melting point **decreases** down the group; density generally **increases** (with an early exception).
They are good conductors of heat and electricity.

Group I – Chemical Properties & Reactivity

All have **one electron in their outer shell**, which they readily lose to form +1 ions.
They react vigorously with water: **2M(s) + 2H₂O(l) → 2MOH(aq) + H₂(g)**.
Reactivity **increases** down the group (Li < Na < K < Rb < Cs < Fr).
Lithium: fizzes, moves on surface; Sodium: more vigorous, melts into a ball; Potassium: burns with a **lilac flame**.
They react with oxygen and water vapour in air, so are **stored under oil**.
Rubidium and caesium react explosively with water; francium is extremely reactive but rare/radioactive.

Group VII (Halogens) – Physical Properties

Halogens are **diatomic** non-metals (F₂, Cl₂, Br₂, I₂, At₂).
All have **seven electrons in their outer shell** and gain one electron to form halide ions.
At room temperature: chlorine is a **pale yellow-green gas**, bromine is a **red-brown liquid**, iodine is a **grey-black solid**.
Melting and boiling points **increase** down the group; density also increases.
Colour **darkens** down the group: fluorine (yellow), chlorine (pale green), bromine (red-brown), iodine (grey-black), astatine (black).
Aqueous solutions: chlorine (very pale green, often colourless), bromine (orange/yellow), iodine (brown).

Group VII – Reactivity & Displacement Reactions

Reactivity **decreases** down the group (opposite to Group I).
A more reactive halogen **displaces** a less reactive halogen from its halide solution.
Chlorine displaces bromine from KBr: **2KBr(aq) + Cl₂(aq) → 2KCl(aq) + Br₂(aq)** (orange colour).
Chlorine displaces iodine from KI: brown colour of iodine appears.
Bromine displaces iodine from KI: brown colour of iodine appears.
No reaction occurs if the halogen is less reactive than the halide (e.g., iodine + KCl).

Transition Elements

Transition elements are metals found in the centre of the Periodic Table (between Group 2 and 3).
They are **hard, strong, lustrous**, and conduct heat and electricity; most have **high melting points** (except mercury).
They **form ions with different charges** (e.g., Fe²⁺ and Fe³⁺) and have **variable oxidation states**.
They form **coloured compounds** (e.g., copper sulfate is blue, copper oxide is black).
They are useful as **catalysts** (e.g., iron in the Haber process).
Scandium and zinc are not considered transition elements as they have only one oxidation state and form colourless compounds.

Noble Gases

Noble gases are in **Group VIII**; they are **monatomic**, colourless gases at room temperature.
They have **very low melting and boiling points** and are **unreactive (inert)**.
Inertness is due to their **full outer electron shells** (e.g., He: 2, Ne: 2,8, Ar: 2,8,8).
Full outer shells mean they have no tendency to gain, lose, or share electrons.
They are used in lighting (neon signs) and as inert atmospheres (argon in welding).

Trends Summary

Group I: reactivity increases down; melting point decreases; density increases (with early exception).
Group VII: reactivity decreases down; melting/boiling point increases; colour darkens; density increases.
Noble gases: all are unreactive; boiling points increase down the group (He lowest, Rn highest).
Transition elements: high melting points, variable oxidation states, coloured compounds, catalytic activity.

Bohr model of sodium (Group I) showing one outer electron.

Bohr model of chlorine (Group VII) showing seven outer electrons.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.How many electrons are in the outer shell of a Group I metal atom?
Easy
- A1
- B2
- C7
- D8
2.Which of the following is a physical property of Group I metals?
Easy
- AThey are hard and strong
- BThey have high melting points
- CThey are soft and easy to cut
- DThey are gases at room temperature
3.What is the trend in reactivity of Group I metals as you go down the group?
Easy
- AReactivity decreases
- BReactivity increases
- CReactivity stays the same
- DReactivity first increases then decreases
4.Which halogen is a red-brown liquid at room temperature?
Easy
- AChlorine
- BBromine
- CIodine
- DFluorine
5.What is the trend in reactivity of Group VII elements as you go down the group?
Easy
- AReactivity increases
- BReactivity decreases
- CReactivity stays the same
- DReactivity first decreases then increases
6.When chlorine water is added to potassium bromide solution, what colour change is observed?
Medium
- AColourless to brown
- BColourless to orange
- COrange to colourless
- DBrown to colourless
7.Which of the following is a characteristic property of transition elements?
Medium
- AThey form colourless compounds
- BThey have only one oxidation state
- CThey form coloured compounds
- DThey are gases at room temperature
8.Why are noble gases unreactive?
Medium
- AThey have a full outer shell of electrons
- BThey have one electron in their outer shell
- CThey are diatomic molecules
- DThey have low melting points

Slides

Group I – The Alkali Metals

Group I metals are called alkali metals because they form alkaline solutions when they react with water.
They all have one electron in their outer shell.
Examples: lithium (Li), sodium (Na), potassium (K).

How many electrons are in the outer shell of a Group I metal?

Physical Properties of Group I Metals

They are soft and easy to cut; they get softer down the group.
They have shiny silvery surfaces when freshly cut.
They conduct heat and electricity.
They have low melting points (some melt on a hot day) and low densities compared to other metals.

Which of these are true about Group I metals?

They have high melting points.
They are soft and easy to cut.
They become softer as you go down the group.
They are stored under oil to prevent reaction with air.

Reactions of Group I Metals with Water

They react to form an alkaline metal hydroxide and hydrogen gas: 2M(s) + 2H₂O(l) → 2MOH(aq) + H₂(g).
Reactivity increases down the group: lithium fizzes slowly, sodium moves rapidly, potassium burns with a lilac flame.
They are stored under oil to prevent reaction with oxygen and water vapour in air.

When sodium reacts with water, the products are sodium hydroxide and ____.

Group VII – The Halogens

Group VII elements are non-metals called halogens.
They are diatomic (form molecules of two atoms): F₂, Cl₂, Br₂, I₂, At₂.
All have seven electrons in their outer shell and gain one electron to form halide ions.

What is the formula of a bromine molecule?

Br
Br₂
Br⁻
Br₂⁻

Physical Properties of Halogens

At room temperature: chlorine is a pale yellow-green gas, bromine is a red-brown liquid, iodine is a grey-black solid.
Melting and boiling points increase down the group.
Colour darkens down the group: fluorine is yellow, chlorine green, bromine red-brown, iodine grey-black, astatine black.

What is the physical state of bromine at room temperature?

Gas
Liquid
Solid
Plasma

Reactivity Trend in Group VII

Reactivity decreases down the group (opposite to Group I).
As you go down, atomic radius increases and electron shielding increases, making it harder to gain an electron.
Fluorine is the most reactive halogen; astatine is the least reactive.

Which statements are correct about halogen reactivity?

Reactivity increases down Group VII.
Fluorine is more reactive than iodine.
Chlorine can displace bromine from a bromide solution.
Iodine can displace chlorine from a chloride solution.

Halogen Displacement Reactions

A more reactive halogen displaces a less reactive halogen from an aqueous halide solution.
Example: chlorine displaces bromine from potassium bromide: 2KBr(aq) + Cl₂(aq) → 2KCl(aq) + Br₂(aq).
The solution turns orange (bromine) or brown (iodine) depending on the halogen displaced.

Chlorine displaces ____ from potassium iodide solution, turning the solution brown.

Transition Elements

Transition elements are metals found in the centre of the Periodic Table between Group 2 and Group 3.
They have typical metallic properties: lustrous, hard, strong, good conductors, high melting points (except mercury).
Unique properties: form ions with different charges (e.g., Fe²⁺ and Fe³⁺), form coloured compounds, and are useful as catalysts.

Which of the following is a property of transition elements but NOT of Group I metals?

They conduct electricity.
They form coloured compounds.
They are soft.
They have low densities.

Noble Gases

Noble gases are in Group VIII (Group 0).
They are monatomic, colourless, gaseous, and have very low melting and boiling points.
They are unreactive (inert) because they have full outer electron shells (e.g., He: 2, Ne: 2,8, Ar: 2,8,8).

Which statements about noble gases are true?

They are diatomic.
They have full outer electron shells.
They are highly reactive.
They are colourless gases at room temperature.

Summary of Trends

Group I: reactivity increases down the group; melting point decreases; density increases.
Group VII: reactivity decreases down the group; melting/boiling point increases; colour darkens.
Transition elements: variable oxidation states, coloured compounds, catalytic properties.
Noble gases: inert due to full outer shells.

Unlock all 40 questions, slides & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

🗂️ Coming soon