Lanthanides – Rare Earth Elements

What are Lanthanides?

Lanthanides (sometimes labeled as Rare Earth elements) are a category of chemical elements in the Periodic Table. Their alternative name “Rare Earths” is derived from the minerals from which Lanthanides can be isolated. However, Lanthanides aren’t rare when it comes to their abundance and they also aren’t Earths in terms of chemical and physical characteristics. Lanthanide elements are the following 15 chemical elements in the Periodic Table: 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).

 

Physical Characteristics of the Lanthanides

Lanthanide elements bear some similar group trends in terms of physical properties, but they aren’t as strong as with other Periodic groups in the Periodic Table. Lanthanides are quite soft and their hardness increases as their atomic numbers progress further down the Periodic Table. These chemical elements have a relatively high resistivity varying between 19 and 134. This resistivity can be compared to the one of a good heat or electrical conductor. Most Lanthanide elements are highly paramagnetic. Heavier Lanthanide elements can become ferromagnetic. The ionic radius of the Lanthanides steadily decreases as their atomic numbers increase further down the Periodic Table. Their melting points and boiling points are relatively high and they vary between 824C and 1652C, and between 1196C and 3520C in their respective order.

 

Chemical Properties of the Lanthanides

In terms of chemical properties Lanthanides are relatively reactive. Some of them are highly reactive and can form oxides when exposed to Oxygen. Lanthanide elements are strong reducing agents and they burn easily in standard air temperature. At extreme conditions they may ignite even burn vigorously. They also react to water and they form ionic compounds. Some Lanthanides have a strong fluorescent hue when they are exposed to ultraviolet light.

 

Bonding and reaction to other elements and compounds

As stated above, Lanthanides are highly reactive to water. Most of them bind with water and they release Hydrogen – slowly in cold water and more vigorously in heated water. At room temperature they also react with dilute acids – a process, which also releases Hydrogen. Lanthanide elements are reactive to most metallic elements and they can form binaries with most Nonmetals. Some Lanthanides produce colorful ions in aqueous solutions – Cerium becomes orange-yellow-ish, Praseodymium can be green or yellow, Neodymium can be violet or blue, Promethium becomes pink, Samarium can be either pale yellow or blood reddish, Terbium could become pale pink or reddish-brown, Holmium becomes yellow, Erbium is rose pink, Thulium shows hues of violet, red and pale green, and Ytterbium may become green-yellowish.

 

Uses and applications of the Lanthanides

These Periodic Table elements have a large application in various industries, including metallurgy, science, synthetics, medicine, lighting installations, optics, phosphor manufacturing, and so forth.

 

The top three applications of the Lanthanides are in catalytic converters, in petroleum refining catalysts, and in magnets. Most of the Lanthanide elements are used in lasers, phosphors and lamps. Lanthanide oxides are also used for night vision goggles and sometimes in sunglasses. Lanthanum and Cerium have found application in medicine as anti-cancer agents. Promethium is used in atomic batteries and luminous paint. Terbium is useful for TV tubes, lamps, and for sonar systems. Erbium is used in dentistry and dermatology as an optical amplifier for lasers in laser surgeries and in dental lasers. Yttrium and Lutetium are used in metallurgy as alloys and catalysts.

 

Lanthanides on Earth

Lanthanide elements are actually quite abundant on Earth, regardless of their alternative name “Rare Earths”. Most of them exist naturally in minerals, while the rest can be found in Monazite sands. Lighter Lanthanides are more abundant in the Earth’s crust, while heavier Lanthanide elements are found in the Earth’s mantle. The radioactive isotopes of Lanthanum, Samarium and Lutetium are also abundant on the Moon and in meteorites.