Rare earths: Periodic table, discovery, exploration in brazil and applications

Abstract

In the ∼150 years comprised between the discovery of yttrium (1794) and promethium (1947), the rare earth metals were an incomplete chapter and a stone in the shoe of the periodic classification of the chemical elements. This group of 17 elements with remarkable chemical similarity raised confusion on many brilliant scientists, including Mendeleev, and led to the consolidation of many theories in Chemistry, from atomic spectroscopy to quantum theory. Nowadays we know that the special properties of these elements arise from filling 4f orbitals, which results in unique spectroscopic, magnetic and catalytic behavior. Such properties make rare earths essential elements on optical devices, lasers, telecommunications and magnetic materials for sustainable energy. The importance of rare earths far exceeds the science and technology domains, reaching the same level of other strategic materials for energy and defense. Hence, this work presents a brief discussion about the historical path of the rare earth elements in the Periodic Table and about the exploration of these resources in Brazil, detailing some of the extractive activities since the 19th century and some perspectives for future activities concerning this group of elements in Brazil.