Definition - What does Lanthanides mean?
Lanthanides are the members of the 15 naturally occurring metallic chemical elements, whose atomic numbers fall between 57 (Lanthanum) and 71 (Lutetium). These elements have their 4f sublevel filled. Lanthanides have similarities in their physical and chemical properties and have many industrial and scientific uses.
Corrosionpedia explains Lanthanides
Any Lanthanide is generally represented by the symbol Ln, which is used to refer to any element in the series. The individual Lanthanides are:
- Lanthanum (La)
- Cerium (Ce)
- Praseodymium (Pr)
- Neodymium (Nd)
- Promethium (Pm)
- Samarium (Sm)
- Europium (Eu)
- Gadolinium (Gd)
- Terbium (Tb)
- Dysprosium (Dy)
- Holmium (Ho)
- Erbium (Er)
- Thulium (Tm)
- Ytterbium (Yb)
- Lutetium (Lu)
Fourteen of the Lanthanides are f-block elements, the fifteenth element, Lutetium, is a d-block element, but considered a Lanthanide since its chemical properties are similar to the other fourteen.
The elements are obtained from naturally occurring minerals. Any Lanthanide mineral contains all the elements. However the concentration of the individual elements may differ depending on the type of mineral. Typical minerals include:
- Xenotime - High concentration of heavier Lanthanides
- Monazite - High concentration of lighter Lanthanides
- Euxenite - Uniform distribution
The silvery-white soft metals share several characteristics. Their hardness increases at higher atomic numbers, exhibits high melting and boiling points, and are strongly paramagnetic. The Lanthanides react with halogen when heated and fluoresce under ultraviolet lights.
Exposure to air causes tarnishing due to the oxidation, which is more rapid in moist air. They are also very reactive and burn easily in air. The elements normally react slowly with oxygen and water, but rapidly at higher temperatures. Other similarities include dissolving quickly in acids, being strong reducing agents and having ionic compounds.
Most Lanthanides are not used in their pure form. They are normally used with other materials or as alloys.
Typical applications include:
- Nuclear plants
- Flints for cigarette lighters
- Catalysts in the production of petroleum and synthetic products
- Lamps, phosphors, X-ray intensifying screens, magnets, lasers and motion picture projectors
- Improving the strength and workability of low-alloy steels
- Corrosion inhibitors