Group 1 (Alkali Metals) (Edexcel GCSE Chemistry)

Revision Note

Test Yourself
Stewart

Author

Stewart

Expertise

Chemistry Lead

Group Classification

  • Elements are arranged on the Periodic table in order of increasing atomic number where each element has one proton more than the element preceding it
  • The table is arranged in vertical columns called groups numbered I – VIII and in rows called periods
  • The period number tells you the number of electron shells an atom has:
    • E.g. elements in period 3 have 3 electron shells

  • The group number tells you how many outer electrons each atom has:
    • E.g. group 6 elements have atoms with 6 electrons in the outermost shell

  • The periodic table positions elements based on their properties which are linked to their electronic configurations
  • Elements with the same number of electrons in the outer shell and hence similar chemical properties are placed in the same group
  • This allows us to use the table to predict the properties of elements based on their position
  • Groups 1, 7 and 0 are elements which have been classified into their respective groups using the periodic table

The periodic table is a road map of all the elements

Physical Properties in Group 1

  • The group 1 metals are known as the alkali metals
    • They form alkaline solutions when they react with water

  • The group 1 metals are lithium, sodium, potassium, rubidium, caesium and francium and they are found in the first column of the periodic table

Group 1 metals in Periodic Table, IGCSE & GCSE Chemistry revision notes

The alkali metals lie on the far left of the periodic table, in the very first group

  • The alkali metals share similar characteristic physical properties
  • Some of these properties are:
    • They are all soft metals which can easily be cut with a knife
    • They have relatively low densities and low melting points
    • They are very reactive (they only need to lose one electron to become highly stable) 

Graph MP Group 1, IGCSE & GCSE Chemistry revision notes

The melting points of the alkali metals

How Alkali Metals React with Water

Reaction with water

  • The reaction of the group 1 metals with water provides evidence for categorising these elements into the same chemical family
  • The general pattern shown is:

group 1 metal + water   metal hydroxide + hydrogen

2M (s) + 2H2O (l) 2MOH (aq) + H2 (g)

      where M is Li, Na, K, Rb or Cs

  • The hydroxides formed all have the same general formula and are colourless, aqueous solutions
  • The metals are so named because they form alkalis in water

Reaction of Sodium with cold water, downloadable AS & A Level Chemistry revision notes

Sodium reacts vigorously with cold water

Exam Tip

Remember the group 1 metals all produce alkaline solutions (>pH 7) when they react with water.Lithium will produce a solution of lithium hydroxide; sodium will produce a solution of sodium hydroxide and so on.Make sure you can give the reaction equations with the correct state symbols to show what is happening during the reactions!

Trends in Group 1

  • Trends are patterns of behaviour in physical or chemical properties
  • Following these trends seen in lithium, sodium and potassium, we can say that:
    • Rubidium, caesium and francium will react even more vigorously with air and water than the first three alkali metals

  • Of the alkali metals, lithium is the least reactive (as it is at the top of group 1) and francium would be the most reactive (as it’s at the bottom of group 1)
  • Using the information given in the trends we would predict that rubidium:
    • would be a soft grey solid
    • would appear shiny when freshly cut
    • would be more dense than potassium (> 0.86 g cm-3)
    • would have a lower melting point than potassium (< 63.5 oC)

Exam Tip

You could be asked to make predictions about how rubidium would be expected to react with water, knowing that it lies below potassium in group 1. Words like 'explosively' and 'violently' would be good ones to choose when describing the reaction.

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Stewart

Author: Stewart

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.