AQA · GCSE · Chemistry
Course version: 8462 · 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.
Going down Group 1 from lithium to sodium to potassium, the atoms have more electron shells, so the outer electron is further from the nucleus and is shielded by more inner shells.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Going down Group 1 from lithium to sodium to potassium, the atoms have more electron shells, so the outer electron is further from the nucleus and is shielded by more inner shells. The attraction between the nucleus and the outer electron is therefore weaker, so the electron is lost more easily. This makes the metals more reactive down the group: lithium reacts steadily with water, sodium reacts vigorously and may melt, and potassium reacts so vigorously that the hydrogen produced often ignites with a lilac flame. The trend can be used to predict that rubidium and caesium would react even more vigorously, sometimes explosively.
What earns the marks
- States that reactivity increases from lithium to sodium to potassium and continues down the group.
- Explains that atoms lower in Group 1 have more electron shells and a larger atomic radius.
- Explains that the outer electron is further from the nucleus and more shielded, so it is lost more easily.
- Links easier loss of the outer electron to increased reactivity down the group.
- Uses the trend to predict that rubidium and caesium react more vigorously than potassium.
- Describes the increasing vigour of reactions with water from lithium to potassium.
Common mistakes and how to put them right
Saying reactivity decreases down Group 1 because atoms get bigger.
Put it right by explaining that the outer electron is lost more easily, so reactivity increases.
Confusing shielding with a stronger nuclear attraction.
Put it right by stating that more inner shells reduce the attraction felt by the outer electron.
Assuming all Group 1 metals react identically with water.
Put it right by describing the increasing vigour from lithium to potassium.
Exam tips
- Always link the trend to the distance and shielding of the outer electron, not just to atomic size.
- Use comparative phrases such as more easily lost and more vigorously when explaining the trend.
- When predicting, name the element and state whether it reacts more or less vigorously than potassium.
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 of the following Group 1 elements is the most reactive?
Listen
Going down Group 1 from lithium to sodium to potassium, the atoms have more electron shells, so the outer electron is further from the nucleus and is shielded by more inner shells. The attraction between the nucleus and the outer electron is therefore weaker, so the electron is lost more easily. This makes the metals more reactive down the group: lithium reacts steadily with water, sodium reacts vigorously and may melt, and potassium reacts so vigorously that the hydrogen produced often ignites with a lilac flame. The trend can be used to predict that rubidium and caesium would react even more vigorously, sometimes explosively. A strong answer earns marks for these points. States that reactivity increases from lithium to sodium to potassium and continues down the group. Explains that atoms lower in Group 1 have more electron shells and a larger atomic radius. Explains that the outer electron is further from the nucleus and more shielded, so it is lost more easily. Links easier loss of the outer electron to increased reactivity down the group. A common slip: Saying reactivity decreases down Group 1 because atoms get bigger. Instead, explaining that the outer electron is lost more easily, so reactivity increases. Exam tip: Always link the trend to the distance and shielding of the outer electron, not just to atomic size.
See it
Key words
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Periodic trends in reactivity
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Atomic structure and electron shells
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Shielding and nuclear attraction
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Prediction from patterns
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See every definition
- Periodic trends in reactivity
- Going down Group 1, the reactivity of the elements increases, so rubidium and caesium would react even more vigorously than potassium.
- Atomic structure and electron shells
- Atoms lower in Group 1 have more electron shells and a larger atomic radius.
- Shielding and nuclear attraction
- More inner shells shield the outer electron, and because it is further from the nucleus the attraction is weaker, so it is lost more easily.
- Prediction from patterns
- The trend can be used to predict that rubidium and caesium react more vigorously than potassium, sometimes explosively.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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