Introduction on Lanthanides
Introduction to the Lanthanides
r understand that lanthanides differ in their properties from the s- and d-block metals; r recall characteristic properties of these elements; r appreciate reasons for their positioning in the Periodic Table; r understand how the size of the lanthanide ions affects certain properties and how this can r understand how to obtain pure samples of individual Ln3+ ions.
1.1 Introduction
Lanthanide chemistry started in Scandinavia. In 1794 Johann Gadolin succeeded in obtaining an ‘earth’(oxide) from a black mineral subsequently known as gadolinite; he called the earth yttria. Soon afterwards, M.H. Klaproth, J.J. Berzelius and W. Hisinger obtained ceria, another earth, from cerite. However, it was not until 1839–1843 that the Swede C.G. Mosander first separated these earths into their component oxides; thus ceria was resolved into the oxides of cerium and lanthanum and a mixed oxide ‘didymia’ (a mixture of the oxides of the metals from Pr through Gd). The original yttria was similarly separated into substances called erbia, terbia, and yttria (though some 40 years later, the first two names were to be reversed!). This kind of confusion was made worse by the fact that the newly discovered means of spectroscopic analysis permitted misidentifications, so that around 70 ‘new’ elements were erroneously claimed in the course of the century. Nor was Mendeleev’s revolutionary Periodic Table a help. When he first published his Periodic Table in 1869, he was able to include only lanthanum, cerium, didymium (now known to have been a mixture of Pr and Nd), another mixture in the form of erbia, and yttrium; unreliable information about atomic mass made correct positioning of these elements in the table difficult. Some had not yet been isolated as elements. There was no way of predicting how many of these elements there would be until Henry Moseley (1887–1915) analysed the X-ray spectra of elements and gave meaning to the concept of atomic number. He
r understand that lanthanides differ in their properties from the s- and d-block metals; r recall characteristic properties of these elements; r appreciate reasons for their positioning in the Periodic Table; r understand how the size of the lanthanide ions affects certain properties and how this can r understand how to obtain pure samples of individual Ln3+ ions.
1.1 Introduction
Lanthanide chemistry started in Scandinavia. In 1794 Johann Gadolin succeeded in obtaining an ‘earth’(oxide) from a black mineral subsequently known as gadolinite; he called the earth yttria. Soon afterwards, M.H. Klaproth, J.J. Berzelius and W. Hisinger obtained ceria, another earth, from cerite. However, it was not until 1839–1843 that the Swede C.G. Mosander first separated these earths into their component oxides; thus ceria was resolved into the oxides of cerium and lanthanum and a mixed oxide ‘didymia’ (a mixture of the oxides of the metals from Pr through Gd). The original yttria was similarly separated into substances called erbia, terbia, and yttria (though some 40 years later, the first two names were to be reversed!). This kind of confusion was made worse by the fact that the newly discovered means of spectroscopic analysis permitted misidentifications, so that around 70 ‘new’ elements were erroneously claimed in the course of the century. Nor was Mendeleev’s revolutionary Periodic Table a help. When he first published his Periodic Table in 1869, he was able to include only lanthanum, cerium, didymium (now known to have been a mixture of Pr and Nd), another mixture in the form of erbia, and yttrium; unreliable information about atomic mass made correct positioning of these elements in the table difficult. Some had not yet been isolated as elements. There was no way of predicting how many of these elements there would be until Henry Moseley (1887–1915) analysed the X-ray spectra of elements and gave meaning to the concept of atomic number. He