Geology And Geophysics

What are Rare Earth Metals

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"Lazy College Professors Never Produce Sufficiently Educated Graduates To Dramatically Help Executives Trim Yearly Losses."  What?! Don't worry, this is just one of the mnemonics that are used to remember the rare earth metals, or the lanthanoids

 Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium,Europium, Gadolinium,Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, and Lutetium are the rare earth metals in question. These metals are in the Lathinide group on the periodic table of elements, with  Scandium and Yttrium added.

Rare earth metals are actually not that rare. They are just more difficult to extract, and some are among the most abundant substances in the Earth's crust. The term Lanthanoid descends from the Greek for "to lie hidden". To lanthanoid, or to lanthanon, or to lanthanide? The current wisdom is to use the suffix "-oid", as this suffix represents similarity among a family of elements. The suffix, "-ide" pertains to negative ions, and "-non" indicates negation or nonexistence.

They have any of five special properties which are catalytic, chemical, electrical, metallurgical, nuclear, magnetic or optical, making rare earth metals valuable for application in a host of advanced technological functions.

These metals range in color from silver to iron gray, and are generally soft, malleable, compoundable and reactive. They are especially reactive when "finely divided" or when heat is applied. The lowest heating point is 798 degrees C for Cerium, with the highest at 1,663 degrees C for Lutetium.

On the Periodic Table of elements, the lanthanoid series is named after Lanthanum, and contains 15 elements that are numbered from 57 through 71. With the exception of lanthanum, which is a d block lanthanoid, the lanthanoids are f-block elements with a corresponding filling of the 4f electron shell.

The term "rare earths" was developed when the 18th century technology was incapable of isolating the lanthanoids from the uncommon oxide type of minerals where they resided. These elements are insoluble in water and are oxides that are part of strongly electropositive metals. Simply put, they could not be smelted at the time. Hence, the term "rare" and "earth".

In relation to the common "earths" such as magnesium and lime, the lanthanoids are rarer, but are very much in abundance in the earth's crust. Cerium, for example is number 26th in abundance in the Earth's crust, while Thulium, the least abundant lanthanoid, is still more abundant than Iodine.

Lanthanoids are found in the base rock of bastnasite, monazite, and loparite and the lateritic ion-adsorption clays.


Wikipedia Dynamic Periodic Table Of Elements

Seeking Alpha, "Rare Earth Metals, Not so Rare"

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