Group I Properties (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)) : Revision Note

Alexandra Brennan

Written by: Alexandra Brennan

Reviewed by: Stewart Hird

Updated on

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  • The Group 1 metals are also called the alkali metals as they form alkaline solutions with high pH values when reacted with water

  • Group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium

  • They all contain just one electron in their outer shell

Physical properties of the Group 1 metals

  • The Group 1 metals:

    • Are soft and easy to cut, getting even softer and denser as you move down the Group (sodium and potassium do not follow the trend in density)

    • Have shiny silvery surfaces when freshly cut

    • Conduct heat and electricity

    • They all have low melting points and low densities compared to other metals, and the melting point decreases as you move down the Group; some would melt on a hot day

    The location of Group 1 in the Periodic Table

    The alkali metals lie on the far left-hand side of the Periodic Table

Chemical properties of the Group I metals

  • They react readily with oxygen and water vapour in air so they are stored under oil to stop them from reacting

  • Group 1 metals will react similarly with water, reacting vigorously to produce an alkaline metal hydroxide solution and hydrogen gas

  • The Group 1 metals get more reactive as you look down the group, so only the first three metals are allowed in schools for demonstrations

Reactions of the Group 1 metals and water

Element

Reaction

Observations

Li

lithium  + water   →   lithium hydroxide  +  hydrogen 

2Li (s)  +  2H2O (l)   →   2LiOH (aq)  +   H2 (g)

  • Relatively slow reaction

  • Fizzing

  • Lithium moves on the surface of the water 

Na

sodium + water   →   sodium hydroxide  +  hydrogen 

2Na (s)  +  2H2O (l)   →   2NaOH (aq)   +   H2 (g)

  • More vigorous fizzing 

  • Moves rapidly on the surface of the water

  • Dissolves quickly 

K

potassium  + water   →   potassium hydroxide  +  hydrogen 

2K (s)  +  2H2O (l)   →   2KOH (aq)  +   H2 (g)

  • Reacts more vigorously than sodium 

  • Burns with a lilac flame 

  • Moves very rapidly on the surface 

  • Dissolves very quickly 

  • As you move down the group:

    • Melting point decreases

    • Density increases

    • Reactivity increases

Predicting the Properties of Group I Elements

  • Knowing the reactions of elements at the top of the group allows you to predict the properties of other elements further down Group 1

Properties of other Alkali Metals (Rubidium, Caesium and Francium)

  • As the reactivity of alkali metals increases down the group, rubidium, caesium and francium will react more vigorously with air and water than lithium, sodium and potassium

  • Lithium will be the least reactive metal in the group at the top, and francium will be the most reactive at the bottom

  • Francium is rare and radioactive so is difficult to confirm predictions

  • For example the reactions with water can be predicted:

Predicting the reaction with water

Element

Observations

Rb

  • Explodes with sparks

Cs

  • Violent explosion due to rapid production of heat and hydrogen

Fr

  • Too reactive to predict 

  • You can also look at other properties such as boiling point, melting point and density of Group 1 elements and use them to predict whether the other properties are likely to be larger or smaller going down the group

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Alexandra Brennan

Author: Alexandra Brennan

Expertise: Chemistry

Alex studied Biochemistry at Newcastle University before embarking upon a career in teaching. With nearly 10 years of teaching experience, Alex has had several roles including Chemistry/Science Teacher, Head of Science and Examiner for AQA and Edexcel. Alex’s passion for creating engaging content that enables students to succeed in exams drove her to pursue a career outside of the classroom at SME.

Stewart Hird

Reviewer: Stewart Hird

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

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