Group 1: The Alkali Metals
Build confidence in Group 1: The Alkali Metals for GCSE Chemistry with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Reactivity increases down Group 1 because the outer electron is further from the nucleus and more easily lost.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Group 1 elements, the alkali metals, all have one electron in their outer shell. This shared arrangement is why they have similar chemical properties.
They are soft, have low densities compared with other metals, and react vigorously with water to produce hydrogen and a metal hydroxide, which is an alkaline solution. Lithium fizzes steadily, sodium melts into a ball and moves rapidly, and potassium ignites with a lilac flame.
Reactivity increases going down the group. This is because the outer electron is further from the nucleus, there is more shielding from inner shells, so the attraction between the nucleus and the outer electron is weaker and it is lost more easily.
Revision notes
Properties and reactions
Alkali metals are soft with low densities. All have one outer shell electron.
With water they produce hydrogen and a metal hydroxide, which is alkaline: lithium + water → lithium hydroxide + hydrogen. With chlorine they form white metal chlorides, and with oxygen they form metal oxides.
Reactivity increasing down the group
Going down the group the outer electron is in a shell further from the nucleus.
There is also more shielding from the inner shells. The attraction between the nucleus and the outer electron is therefore weaker, so the electron is lost more easily and the metal is more reactive.
Observations with water
Lithium: fizzes steadily and moves on the surface. Sodium: melts into a ball and moves rapidly, fizzing.
Potassium: ignites, burning with a lilac flame. The increasingly vigorous reaction demonstrates the reactivity trend directly.
Key points
- Group 1 metals have one outer shell electron.
- They are soft with low densities.
- They react with water to give hydrogen and a hydroxide.
- The hydroxide solution is alkaline.
- Reactivity increases down the group.
- The outer electron is lost more easily further down.
Worked examples
Example 1
Write the word equation for the reaction of sodium with water. [2 marks]
Model answer
Sodium + water → sodium hydroxide + hydrogen. Correct reactants (1 mark). Correct products (1 mark).
Example 2
Explain why reactivity increases down group 1. [3 marks]
Model answer
Going down the group, the outer electron is in a shell further from the nucleus (1 mark), and there is more shielding from the inner shells (1 mark). The attraction between the nucleus and the outer electron is therefore weaker, so it is lost more easily and the metal reacts more readily (1 mark).
Example 3
Describe what you would observe when potassium is added to water. [2 marks]
Model answer
It reacts vigorously, fizzing and moving on the surface (1 mark), and ignites, burning with a lilac flame (1 mark).
Common mistakes
Saying reactivity decreases down group 1.
It increases, because the outer electron is lost more easily.
Forgetting hydrogen as a product.
The reaction with water gives both a metal hydroxide and hydrogen.
Explaining reactivity by atom size alone.
Mention distance from the nucleus AND shielding for full marks.
Saying the solution is acidic.
Metal hydroxides give alkaline solutions, which is why they are alkali metals.
Exam tips
- Always give both distance and shielding in reactivity explanations.
- Learn the observations for lithium, sodium and potassium.
- Remember hydrogen is always a product with water.
- Say alkaline when describing the resulting solution.
Key terms
- Alkali metal
- A group 1 element with one outer shell electron.
- Shielding
- The blocking of nuclear attraction by inner electron shells.
- Metal hydroxide
- An alkaline compound formed when a metal reacts with water.
- Reactivity
- How readily an element takes part in chemical reactions.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.