AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
In Group 1, the reactivity of the elements increases going down the group.
Full specification wording
Group 1: In Group 1, the reactivity of the elements increases going down the group.
Group 1 metals, the alkali metals, each have one electron in their outer shell.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 5
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Group 1 metals, the alkali metals, each have one electron in their outer shell. Going down the group from lithium to sodium to potassium, the atoms gain extra inner shells, so the outer electron is further from the nucleus and is shielded by more inner electrons. The force of attraction between the nucleus and the outer electron therefore weakens, so the outer electron is lost more easily. Reactivity is judged by how readily the metal loses that outer electron to form a 1⁺ ion, so reactivity increases down the group.
For example: Lithium fizzes steadily in water, sodium reacts more vigorously and may melt, and potassium reacts so vigorously that the hydrogen produced ignites with a lilac flame.
What earns the marks
- State that Group 1 elements have one electron in their outer shell and form 1⁺ ions by losing it.
- Explain that going down the group the outer electron is in a shell further from the nucleus.
- Explain that increased shielding by inner shells and greater distance reduce the attraction between the nucleus and the outer electron.
- Conclude that the outer electron is lost more easily down the group, so reactivity increases.
- Support the trend with a comparison of reactions with water, such as lithium fizzing gently while potassium ignites.
Common mistakes and how to put them right
Saying reactivity decreases down Group 1 because atoms get bigger.
Put it right: Bigger atoms lose the outer electron more easily, so reactivity increases.
Confusing Group 1 with Group 7, where reactivity decreases down the group.
Put it right: The two trends run in opposite directions.
Claiming the outer electron is pulled away by water.
Put it right: The electron is lost because the attraction from the nucleus is weaker, and water is the reactant that accepts it in the reaction.
Exam tips
- Link each step of the explanation to the structure of the atom: outer shell, distance and shielding.
- Use the phrase 'outer electron is lost more easily' rather than vague wording such as 'more reactive'.
- When asked to compare, name two specific metals and describe the difference in their reactions with water.
Try the lesson
The start of the Group 1: In Group 1, the reactivity of the elements increases going down the group. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes the trend in reactivity of the Group 1 elements?
Listen
Group 1 metals, the alkali metals, each have one electron in their outer shell. Going down the group from lithium to sodium to potassium, the atoms gain extra inner shells, so the outer electron is further from the nucleus and is shielded by more inner electrons. The force of attraction between the nucleus and the outer electron therefore weakens, so the outer electron is lost more easily. Reactivity is judged by how readily the metal loses that outer electron to form a 1⁺ ion, so reactivity increases down the group. For example, lithium fizzes steadily in water, sodium reacts more vigorously and may melt, and potassium reacts so vigorously that the hydrogen produced ignites with a lilac flame. A strong answer earns marks for these points. State that Group 1 elements have one electron in their outer shell and form 1⁺ ions by losing it. Explain that going down the group the outer electron is in a shell further from the nucleus. Explain that increased shielding by inner shells and greater distance reduce the attraction between the nucleus and the outer electron. Conclude that the outer electron is lost more easily down the group, so reactivity increases. A common slip: Saying reactivity decreases down Group 1 because atoms get bigger. Instead, bigger atoms lose the outer electron more easily, so reactivity increases. Exam tip: Link each step of the explanation to the structure of the atom: outer shell, distance and shielding.
Key words
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Group 1 alkali metals
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Trends in reactivity
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Formation of 1⁺ ions
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See every definition
- Group 1 alkali metals
- Metals in Group 1 that each have one electron in their outer shell.
- Trends in reactivity
- Going down the group, reactivity increases because the outer electron is lost more easily.
- Formation of 1⁺ ions
- Reactivity is judged by how readily the metal loses its outer electron to form a 1⁺ ion.
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