Lanthanides early history

The lanthanide family of elements has played an important role which can be expected to continue in the development of coordination chemistry. In the early history of these elements, their close chemical similarity in the stable tripositive oxidation state made the task of achieving high purity for individual elements very difficult Although the entire lanthanide series had been discovered by 1907 (with the exception of Pm) and mixtures of lanthanides had been found in more than a hundred minerals, it was not until efficient separation methods were developed that detailed and diverse studies of their coordination chemistry could be undert en. 

While the history of the discovery and the separation of the rare earths is well documented, the story of the accommodation of the rare earths in the periodic table is less well known. Part of the story can be found in the famous book on the periodic system of van Spronsen (1969), but recent investigations in the field of the history and philosophy of chemistry have shed new light on the early episodes of the development of the periodic system after 1869. Moreover, the accommodation of the rare earths in the periodic table is still an active research topic. In 2008 and 2009, there was a debate in the Journal of Chemical Education on the position of the lanthanides and actinides in the periodic table (Clark and White, 2008 Lavelle, 2008a,b, 2009 Stewart, 2008 Jensen, 2008b, 2009 Clark, 2008 Scerri, 2009a Laing, 2009). 

The historical development of d- and f-hlock element chemistry also reflects their various chemical and physical properties. Metals occurring in elemental form were discovered early in human history, whereas chemically similar elements such as the lanthanides have only relatively recently been identified as separate elements. 

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