Foreword for PAC special issue 4th International Conference on the Periodic Table (Mendeleev 150)

The conference Mendeleev 150 was held to join the worldwide celebrations of the 150th Anniversary of the publication of Dmitri I. Mendeleev’s Periodic Table of Chemical Elements and the International Year of the Periodic Table proclaimed by the United Nations. The presentations of the invited speakers were published by the Journal of Pure and Applied Chemistry as a special issue. The papers in this issue formed a broad picture of the Periodic Table: the history, the people, the reasoning, the mathematical description of the law, and the efforts to predict and to create any new elements. The highlights of the presentations are briefly introduced in this article as the Preface to the special issue.