AQA · GCSE · Combined Science

    Course version: 8464 · Version from Sept 2018

    Explain how the reactions of elements are related to the arrangement of…

    Full specification wording

    Metals and non-metals: explain how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number.

    An element's reactions depend on how easily its atoms gain, lose or share electrons, governed by its electron arrangement.

    Checked against the AQA 8464 specification (opens in a new tab) on .

    • Point 6 of 6
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    An element's reactions depend on how easily its atoms gain, lose or share electrons, governed by its electron arrangement. Atoms react to reach a stable outer shell, usually eight electrons (two for the first shell). Metals, such as sodium (2,8,1), lose their single outer electron to form Na⁺ ions. Non-metals, such as chlorine (2,8,7), gain or share electrons to complete an outer shell. For Groups 1 to 7, the group number equals the number of outer electrons. Since atomic number determines the total number of electrons and their arrangement, it dictates the pattern of reactivity.

    For example: Group 1 elements all have one outer electron and react similarly, with reactivity increasing down the group as the electron is lost more easily.

    What earns the marks

    • Reactions of elements are determined by the number and arrangement of electrons, especially the outer-shell electrons.
    • Atoms react to achieve a stable outer electron arrangement, typically eight electrons (two for the first shell).
    • Metals lose outer electrons to form positive ions, for example Na → Na⁺ + e⁻.
    • Non-metals gain or share electrons to complete their outer shell, for example chlorine gaining one electron to form Cl⁻.
    • For Groups 1 to 7, the group number equals the number of outer electrons, so elements in the same group react similarly.
    • Atomic number gives the number of protons and hence the number of electrons, so it determines the electron arrangement and the reactivity pattern.

    Common mistakes and how to put them right

    • Saying reactivity depends only on the number of shells rather than the outer-shell arrangement.

      Put it right by linking reactivity to outer electrons and the drive for a stable shell.

    • Writing that atoms 'want' or 'need' eight electrons without explaining electron transfer or sharing.

      Put it right by describing loss, gain or sharing of electrons to reach a stable arrangement.

    • Confusing atomic number with mass number when explaining electron arrangement.

      Put it right by stating atomic number equals the number of protons and electrons in a neutral atom.

    Exam tips

    • Link each statement to a specific group, such as Group 1 metals losing one electron or Group 7 non-metals gaining one electron.
    • When explaining a group trend, do not compare outer-shell electron numbers as they are identical; instead, compare the number of shells, distance from the nucleus, shielding, and ease of electron loss or gain.

    Try the lesson

    The start of the Metals and non-metals: explain how the reactions of elements are related to the arrangement of electrons in their atoms and hence to their atomic number. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Sodium reacts vigorously with water, but argon does not react with water at all. Which statement best explains this difference?

    Listen

    An element's reactions depend on how easily its atoms gain, lose or share electrons, governed by its electron arrangement. Atoms react to reach a stable outer shell, usually eight electrons (two for the first shell). Metals, such as sodium (2,8,1), lose their single outer electron to form Na⁺ ions. Non-metals, such as chlorine (2,8,7), gain or share electrons to complete an outer shell. For Groups 1 to 7, the group number equals the number of outer electrons. Since atomic number determines the total number of electrons and their arrangement, it dictates the pattern of reactivity. For example, Group 1 elements all have one outer electron and react similarly, with reactivity increasing down the group as the electron is lost more easily. A strong answer earns marks for these points. Reactions of elements are determined by the number and arrangement of electrons, especially the outer-shell electrons. Atoms react to achieve a stable outer electron arrangement, typically eight electrons (two for the first shell). Metals lose outer electrons to form positive ions, for example Na → Na⁺ + e⁻. Non-metals gain or share electrons to complete their outer shell, for example chlorine gaining one electron to form Cl⁻. A common slip: Saying reactivity depends only on the number of shells rather than the outer-shell arrangement. Instead, linking reactivity to outer electrons and the drive for a stable shell. Exam tip: Link each statement to a specific group, such as Group 1 metals losing one electron or Group 7 non-metals gaining one electron.

    See it

    A top-down flowchart. Atomic number leads to number of electrons, which leads to electron arrangement, which leads to outer-shell electrons. From outer-shell electrons there are three branches. The first branch goes to metals lose outer electrons, which leads to positive ions, e.g. Na to Na+. The second branch goes to non-metals gain or share electrons, which leads to complete outer shell, e.g. chlorine to Cl-. The third branch goes to group number equals outer electrons for Groups 1 to 7, which leads to elements in the same group react similarly.
    It shows how atomic number determines electron arrangement and outer-shell electrons, which in turn decide whether metals lose electrons and non-metals gain or share them, and why elements in the same group react similarly.

    Key words

    Say what each word means before you turn the card.

    Atomic number

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    Outer-shell electrons

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    Stable outer electron arrangement

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    Positive ions

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    See every definition
    Atomic number
    Gives the number of protons and hence the number of electrons, so it determines the electron arrangement and the reactivity pattern.
    Outer-shell electrons
    For Groups 1 to 7, the group number equals the number of these, and reactions are determined especially by them.
    Stable outer electron arrangement
    What atoms react to achieve, typically eight electrons, or two for the first shell.
    Positive ions
    Formed when metals lose outer electrons, for example Na → Na⁺ + e⁻.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. Atomic number leads to number of electrons, which leads to electron arrangement, which leads to outer-shell electrons. From outer-shell electrons there are three branches. The first branch goes to metals lose outer electrons, which leads to positive ions, e.g. Na to Na+. The second branch goes to non-metals gain or share electrons, which leads to complete outer shell, e.g. chlorine to Cl-. The third branch goes to group number equals outer electrons for Groups 1 to 7, which leads to elements in the same group react similarly.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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