Lantanoider

Lantanoider, also known as lanthanides or lanthanoids in many languages, is the term for a group of fifteen metallic elements with atomic numbers 57 through 71: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. They are the f-block elements that sit at the bottom of the periodic table and are usually discussed together as a family due to their similar chemistry.

Chemically, lantanoider share many properties because their 4f electrons are highly shielded by inner shells, leading to gradual changes across the series. They predominantly form a +3 oxidation state; some have accessible +2 or +4 states (notably Ce, Eu, and Yb). They are typically soft, silvery metals that tarnish in air and react slowly with water and oxygen.

Occurrence and extraction: They occur together in mineral deposits such as monazite and bastnäsite; commercially extracted through complex processes including flotation, acid processing, and solvent extraction. Primary producers have included China, Australia, the United States, and India; the supply chain is influenced by geopolitical and environmental considerations.

Applications: Nd-Fe-B magnets rely on Nd and Pr; CeO2 and other lanthanide oxides are used as catalysts and in automotive catalysts; lanthanide-doped phosphors (e.g., Eu, Tb) enable lighting and display technologies; Gd and other lanthanides are used in MRI contrast agents; Nd:YAG and other lasers are used in industrial and medical applications.

History and naming: The lanthanide group was first identified in the 19th century, with Mosander isolating elements in the late 1830s; the name lanthanide derives from Greek lanthanein "to lie hidden," reflecting their late discovery. In some languages, lantanoider is used to refer to this group.