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Group I properties IGCSE Notes

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IGCSE Chemistry Notes  Group I Alkali Metals

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Reactions of Group 1 Elements with Water
1. Introduction

Introduction to Group I Alkali Metals

What are Group I elements?

Group I elements are called alkali metals. They are found in the first column of the Periodic Table.
  • Lithium (Li)
  • Sodium (Na)
  • Potassium (K)
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Outer electron and ion formation

All Group I elements have 1 electron in the outer shell.
  • Lithium: 2,1
  • Sodium: 2,8,1
  • Potassium: 2,8,8,1
Na  ->  Na+ + e-
Because they have one outer electron, they easily lose it to form +1 ions.
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2. Physical Properties

Physical properties of lithium, sodium and potassium

(a) Soft metals

  • Can be cut easily with a knife
  • Freshly cut surface is shiny
  • Quickly becomes dull in air
Trend: metals become softer down the group.
Lithium -> harder ;   Sodium -> softer  ;   Potassium -> even softer
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(b) Low melting points

Element Approx. melting point
Lithium 180°C
Sodium 98°C
Potassium 63°C
Trend: melting point decreases down the group.
Li > Na > K
As atomic size increases, attraction between metal ions and electrons becomes weaker, so less energy is needed to melt the metal.
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(c) Density

Element Density
Lithium 0.53 g/cm3
Sodium 0.97 g/cm3
Potassium 0.86 g/cm3
  • They are low-density metals
  • Lithium, sodium and potassium float on water
Trend: density generally increases down the group.
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3. Chemical Property

Reactivity of Group I metals

Why they are reactive

Group I metals are very reactive metals.
  • They react easily with water
  • They react easily with oxygen
  • They react easily with halogens
Because they are very reactive, they are stored in oil to prevent reaction with air or water.
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Reaction with water

General reaction:
Metal + Water ? Metal hydroxide + Hydrogen
2Na + 2H2O -> 2NaOH + H2
Trend: reactivity increases down the group.
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Observations when added to cold water

Metal Observation
Lithium Fizzes slowly
Sodium Melts into a ball and moves quickly
Potassium Reacts violently and burns with a lilac flame
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4. Trends

Summary of trends down Group I

Property Trend down Group I
Atomic size Increases
Density Generally increases
Melting point Decreases
Softness Increases
Reactivity Increases
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5. Prediction

Predicting the properties of other Group I elements

Using the trend

We can use Group I trends to predict the properties of other alkali metals such as rubidium (Rb) and caesium (Cs).
  • More reactive than potassium
  • Lower melting point than potassium
  • Very soft metals
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Example prediction

Caesium reacts very violently with water and is even more reactive than potassium.
This matches the trend that reactivity increases down Group I.
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Exam Summary

Key exam points to remember

Group I metals have one outer electron
They form +1 ions
They are soft metals
Melting point decreases down the group
Density generally increases down the group
Reactivity increases down the group
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Syllabus Objectives

CORE:

  • Describe the Group I alkali metals, lithium, sodium and potassium, as relatively soft metals with general trends down the group, limited to:
  • (a) decreasing melting point
  • (b) increasing density
  • (c) increasing reactivity
  •  Predict the properties of other elements in Group I, given information about the elements

Revision Notes

IGCSE Chemistry Notes Group I properties

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Topic: Group I Elements / Test Your Understanding

Study the table carefully, then click the highlighted answer spaces to reveal the correct answers.

1 Information Table

The table below gives some information about the elements in Group I of the Periodic Table.

element boiling point / °C density / g cm?3 radius of atom in the metal / nm reactivity with water
lithium 1342 0.53 0.157  
sodium 883 0.97 0.191 rapid
potassium 760 0.86 0.235 very rapid
rubidium   1.53 0.250 extremely rapid
caesium 669 1.88   explosive

2 Answer the Questions

(a) How does the density of the Group I elements change down the Group?
Click to reveal answer Increases overall down the group, although the trend is not perfectly regular.
(b) Suggest a value for the boiling point of rubidium.
Click to reveal answer Approximately 686°C. Acceptable range: 670–714°C.
(c) Suggest a value for the radius of a caesium atom.
Click to reveal answer Approximately 0.272 nm. Acceptable range: 0.260–0.300 nm.
(d) Use the information in the table to suggest how fast lithium reacts with water compared with the other Group I metals.
Click to reveal answer Lithium reacts more slowly than sodium and the other Group I metals. Accept: slow, slower, less rapid, or gently.
(e) State three properties shown by all metals.
Click to reveal answer Any three from: conduct electricity, conduct heat, malleable, ductile, shiny, sonorous, solid at room temperature.

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IGCSE Chemistry Revised Syllabus Notes[ 2023-2025 exams]

1-States of matter

2 Atoms, elements and compounds

3 Stoichiometry

4 Electrochemistry

5 Chemical energetics

6 Chemical reactions

7 Acids, bases and salts

8 The Periodic Table

9 Metals

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10 Chemistry of the environment

11 Organic chemistry

12 Experimental techniques and chemical analysis