The Rare Earths crisis

[johnmarks9]

Dear Mark,

Many thanks for posting the fascinating history of the Periodic Table´s “Rare Earths crisis”. [1]: a very enjoyable read.

In 1870, Mendeleyev´s “primary elements” viz. the transition series and the rare earth series, clearly foreshadow Sommerfeld´s “A” and “B” subgroups. In 1871 Mendeleyev abandoned this “Attempted System” for his “Natural System” integrating the transition series with the main groups. In his homologous accommodation methodology (“the Mendeleyev Method”) he bravely attempted the same for the rare earths, successfully placing lanthanum, cerium and praseodymium and predicted a total of 17 (if you include Sc, Y & Lu) rare earths. Ironically, Brauner´s valiant but frustrated efforts with the lanthanides would have succeeded with the actinides.

[1] Thyssen P, Binnemans K: "Accommodation of the Rare Earths in the Periodic Table" 2011.