A group of elements that include SCANDIUM; YTTRIUM; and the LANTHANOID SERIES ELEMENTS. Historically, the rare earth metals got their name from the fact that they were never found in their pure elemental form, but as an oxide. In addition, they were very difficult to purify. They are not truly rare and comprise about 25% of the metals in the earth's crust.
Odkazy
(1) - KNIHY
predmetové heslo
openseadragon
Počet záznamov: 1
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