AQA · GCSE · Chemistry

    Course version: 8462 · Version from Sept 2018

    Students should be able to describe these steps in the development of the…

    Full specification wording

    Development of the periodic table: Students should be able to describe these steps in the development of the periodic table.

    The periodic table developed through several stages.

    Checked against the AQA 8462 specification (opens in a new tab) on .

    • Point 6 of 6

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    The periodic table developed through several stages. Early chemists such as Newlands and Döbereiner noticed patterns, but Mendeleev produced the version that shaped later work. He arranged elements mainly by relative atomic weight, placed elements with similar properties into groups, and left gaps for elements he predicted were undiscovered. When gallium and germanium were later found with properties close to his predictions, confidence in the table grew. Later work on atomic structure showed that proton number, not atomic weight, gives the correct order, and this resolved anomalies such as argon before potassium. The modern table arranges elements by increasing proton number, with groups showing similar properties and periods showing repeating trends.

    What earns the marks

    • Describe early attempts to find patterns among elements, including ordering by relative atomic weight.
    • Describe Mendeleev arranging elements by atomic weight and grouping those with similar properties.
    • Describe Mendeleev leaving gaps and predicting properties of undiscovered elements.
    • Describe how later discovery of predicted elements supported the table.
    • Describe the modern change to ordering by proton number, which resolved anomalies.

    Common mistakes and how to put them right

    • Crediting Mendeleev with ordering by proton number.

      Put it right by stating he used atomic weight and that proton number came later.

    • Saying Mendeleev left gaps because he had no data.

      Put it right by explaining the gaps were for elements not yet discovered.

    • Treating the periodic table as a single invention.

      Put it right by describing it as a sequence of improvements over time.

    Exam tips

    • Use a clear sequence: early patterns, Mendeleev's table, predictions, later proton-number ordering.
    • Name at least one predicted element, such as gallium or germanium, to support the description.
    • Keep the account chronological so the examiner can follow the development.

    Try the lesson

    The start of the Development of the periodic table: Students should be able to describe these steps in the development of the periodic table. lesson, made from checked teaching notes for this specification point.

    Have a go first

    In the development of the periodic table, what did early scientists first do to arrange the known elements?

    Listen

    The periodic table developed through several stages. Early chemists such as Newlands and Döbereiner noticed patterns, but Mendeleev produced the version that shaped later work. He arranged elements mainly by relative atomic weight, placed elements with similar properties into groups, and left gaps for elements he predicted were undiscovered. When gallium and germanium were later found with properties close to his predictions, confidence in the table grew. Later work on atomic structure showed that proton number, not atomic weight, gives the correct order, and this resolved anomalies such as argon before potassium. The modern table arranges elements by increasing proton number, with groups showing similar properties and periods showing repeating trends. A strong answer earns marks for these points. Describe early attempts to find patterns among elements, including ordering by relative atomic weight. Describe Mendeleev arranging elements by atomic weight and grouping those with similar properties. Describe Mendeleev leaving gaps and predicting properties of undiscovered elements. Describe how later discovery of predicted elements supported the table. A common slip: Crediting Mendeleev with ordering by proton number. Instead, stating he used atomic weight and that proton number came later. Exam tip: Use a clear sequence: early patterns, Mendeleev's table, predictions, later proton-number ordering.

    See it

    A vertical flowchart with ten boxes connected by downward arrows. The first box says early chemists notice patterns. An arrow leads to Mendeleev arranging elements mainly by relative atomic weight. The next box says elements with similar properties placed in groups, then gaps left for undiscovered elements, then Mendeleev predicts properties of undiscovered elements. An arrow leads to gallium and germanium found with properties close to predictions, then confidence in the table grows. The next box says later work on atomic structure shows proton number gives correct order, then anomalies such as argon before potassium resolved, and finally the modern table arranges elements by increasing proton number.
    The sequence of stages in the development of the periodic table, from early pattern-finding through Mendeleev's predictions to the modern ordering by proton number.

    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 vertical flowchart with ten boxes connected by downward arrows. The first box says early chemists notice patterns. An arrow leads to Mendeleev arranging elements mainly by relative atomic weight. The next box says elements with similar properties placed in groups, then gaps left for undiscovered elements, then Mendeleev predicts properties of undiscovered elements. An arrow leads to gallium and germanium found with properties close to predictions, then confidence in the table grows. The next box says later work on atomic structure shows proton number gives correct order, then anomalies such as argon before potassium resolved, and finally the modern table arranges elements by increasing proton number.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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