Topic outline

  • General

    The lanthanides and actinides

    This website is home to a multimedia activity on the Lanthanides and Actinides, elements 57-70 and 89 - 102 of the Periodic Table. The lanthanide and actinide elements
    Glenn Seaborg

    Within these pages you will find images of the elements and videos of some reactions but the major story concerns the work of Glenn Seaborg and his endeavours to work out just where in the Periodic Table these elements should be placed.

    We interviewed Seaborg in the 1970's and at various points in the activity he tells the story of the work which earned him his Nobel prize in 1951 (Nobel website).

    This is an interactive multimedia activity that involves you in evaluating the competing arguments about the structure of the Periodic Table that arose from discoveries made in the first half of the 20th century. Consequently you will be asked questions as the activity progresses. To follow the argument and answer these questions you will need to have an understanding of the oxidation states of elements. These questions are not a formal test - no-one will look at your answers and mark you - but they are there to engage you and we hope you enjoy the challenge.

    • Topic 1

      1 Introduction

      You will need an understanding of highest oxidation states to understand the problem that is posed in the Introduction. OU students are provided with other interactive programs but these are not on this site.

      Click on this link The lanthanides and actinides multimedia activity to start. The activity will open in a new tab or window.

      • Topic 2

        2 The lanthanides

        Here you will find photographs of all the lanthanide metals and videos of their reactions with dilute hydrochloric acid. The oxidation states displayed hold the key to why these elements are treated as a block.

        If you have the activity open in another tab or window return to it now or click here to start it.

        • Topic 3

          3 Classifying the trans-uranium elements

          Actinium, thorium, protactinium and uranium are introduced, but where do they fit into the Periodic Table. We introduce the ideas of Alfred Werner but once again concentrate of highest oxidation states. Alfred Werner

          If you have the activity open in another tab or window return to it now or click here to start it.

          • Topic 4

            4 Electronic configuration

            Niels Bohr What contribution did electronic configuration make to the debate on the Structure of the Periodic Table ? In the 1920s, the man best placed to make such a contribution was the great physicist, Niels Bohr.

            If you have the activity open in another tab or window return to it now or click here to start it.

            • Topic 5

              5 Making trans-uranium elements: the first moves

              You might think that Nobel laureates are exceptional people, and indeed they are. But here Seaborg is suitably candid about himself:

              "...I bought the theory (of Hahn and Strassman and Meitner) hook, line and sinker..."

              only later to realise

              "...I just thought to myself, my god how stupid can a person be?..."

              If you have the activity open in another tab or window return to it now or click here to start it.

              • Topic 6

                6 Making trans-uranium elements: the second round

                Edwin Macmillan quite accidentally finds a way to separate the trans-uranium elements from the fission soup produced when uranium solutions are bombarded with neutrons. Edwin Macmillan

                If you have the activity open in another tab or window return to it now or click here to start it.

                • Topic 7

                  7 Element 94

                  Element 94 is plutonium and here you will see the three common oxidation states of plutonium.

                  If you have the activity open in another tab or window return to it now or click here to start it.

                  • Topic 8

                    8 The actinide hypothesis

                    Seaborg describes the work leading up to the actinide hypothesis which appeared in the December 1945 issue of the Chemical and Engineering News. In this article he proposed his new method of putting these heavy elements in the Periodic Table.

                    If you have the activity open in another tab or window return to it now or click here to start it.

                    • 9 Conclusion If you have the activity open in another tab or window return to it now or click here to start it.

                      • References

                      • Video library