Intro to Lanthanides
What are the lanthanides, aka rare earth elements? The lanthanide series is a row of elements situated below the main block of the periodic table, within the f block along with the actinides. They are all metals. Lanthanides occupy elements 57-71 and branch off after barium on the periodic table. Their electron configurations are much like the transition metals, but with a fourth electron shell that can hold 18 electrons. They possess similar properties to transition metals but have some unique characteristics and applications. The lanthanides, along with scandium and yttrium, are known as the rare-earth elements.
Characteristic Properties of Lanthanides
- Lanthanides are commonly found in earth’s crust as compounds with other metals
- Lanthanides are reactive and form ionic compounds with nonmetals
- Lanthanides tarnish, meaning they quickly lose their shine/luster when exposed to air
- Lanthanides are stored in oil or in noble gases to prevent tarnishing
- Lanthanides are solid STP
- Most lanthanides only use three electrons as valence electrons
- Rare earth elements are quite difficult to tell apart, as they have similar physical and chemical properties
- Rare earth elements have unique electronic and magnetic properties, which allows them to occupy special niches in technology
Are Lanthanides Metals?
Absolutely! All of the rare-earth elements are metals with strong metallic properties, a metallic luster and a silvery look.
Are the Rare Earth Elements Rare?
Rare earth elements are not particularly rare. Cerium is the 25th most abundant element in the earth’s crust, more common than copper.
Monazite is a group of minerals that contain the highest concentration of rare earth elements. Monazite usually contains the phosphate of cerium, lanthanum, neodymium, samarium, and/or praseodymium. It also often contains thorium, and sometimes uranium, which makes it radioactive. Monazite is found in Brazil, India, South Africa, Australia and the USA. Extracting rare earth elements from Monazite is an extensive process, requiring many filtrations and neutralizations.
How many Rare Earth Elements are there?
So how many rare earth elements actually exists? The answer is 15 or 17, depending on how you define a rare earth element. If you include Scandium and Yttrium, there are 17. If you don’t, and any include true lanthanides, than there are only 15 rare earths. The reason scandium and yttrium are often included, is because their physical and chemical properties are similar to true lanthanides, and they are found in the same ores.
A List of Lanthanide Elements
Lanthanum – Element 57
The name Lanthanum comes from the Greek word Lanthanein, which means “hidden”. It was discovered by Swedish Chemist Carl Gustaf Masander in 1839. It is soft enough to be cut with a knife, ductile, and has a silvery color. Lanthanum has numerous industrial uses, including the ignition of torches, lighters, and blowpipes. It is also used in electron cathodes and lightbulbs to prevent yellow light from being emitted.
Cerium – Element 58
Cerium has physical properties similar to lanthanum and has a similar appearance as well. It is by far the most abundant lanthanide in the earth’s crust. Cerium was discovered by German chemist Martin Heinrich Klaproth in 1803. It is named after the dwarf planet Ceres, which orbits the sun between Mars and Jupiter. Cerium readily reacts with water and the halogen elements. Cerium-based compounds are used to polish glass, but are also used in catalytic converters and LED lights to produce white.
Praseodymium – Element 59
Praseodymium has similar physical characteristics to cerium and lanthanum, a pattern that will continue throughout our survey of the lanthanides. However, it has much more potent optical, electrical, and magnetic properties. It is too reactive to occur naturally in its pure elemental form. Praseodymium was discovered by Austrian chemist Baron Carl Aur von Welsbach while separating differently colored salts. Unlike many other rare-earth metals, praseodymium is paramagnetic at all temperatures. Praseodymium is used in a wide variety of applications, from ceramic stains to wind turbines to high-powered magnets.
Neodymium – Element 60
Neodymium shares many physical and chemical properties with the former lanthanides, but unlike its periodic table companions, Neodymium is capable of displaying multiple colors through multiple oxidation states. It produces pink, blue, and yellow in the oxidation states of +2, +3, +4 respectively. Most of the naturally occurring neodymium on earth is in eastern Asia. It was also discovered by Welsbach in 1885. The most significant use of Neodymium is in electronics. Neodymium is able to form strongly magnetic alloys with other metals. These alloys are used in a wide array of modern technologies, such as speakers, microphones, and headphones. Large neodymium-based magnets are found in the electric motors of hybrid cars. Neodymium is one of the most influential and important elements of the 21st-century economy!
Promethium – Element 61
Promethium is one of the rarest elements on earth. It is estimated that there are only about 500 grams worldwide occurring in the earth’s crust. However, it can be produced in a laboratory by bombarding Uranium-235 with neutrons at very high speeds. This process produces Promethium-147, the only isotope of the element with practical applications. It was first synthesized by mistake at Oak Ridge National Lab in Tennessee in 1945. Relatively little chemistry is known regarding promethium because it is so unstable and thus difficult to study. Outside of research, the only use of promethium is in atomic batteries.
Samarium – Element 62
Samarium has the. same silvery luster as its fellow lanthanides, but is much harder and somewhat more ductile. It also oxidizes in air, but much more slowly. Samarium is found in some parts of the earth’s crust with a concentration as high as 3%, making it relatively abundant. French chemist Paul-Emile Lecoq de Boisbaudran discovered, isolated, and named the element in 1879. Like its cousin element neodymium, samarium is used to construct high-powered magnets, but samarium-based magnets are capable of withstanding much greater temperatures.
Europium – Element 63
Europium is by far the most reactive lanthanide. Its high reactivity requires it to be stored within inert fluids to prevent it from reacting with air. Europium readily reacts with all halogens and forms stable compounds with chalcogens. Like samarium, it was discovered by Boisbaudran in 1892. Unlike samarium, it is very soft and malleable. Europium is one of the rarest elements on earth. Pure europium does not exist in nature. It must be mined from minerals such as monazite. Europium does not have as numerous applications as other lanthanides, but it is used in many optoelectronic devices, such as lasers and fluorescent lamps.
Gadolinium – Element 64
Gadolinium possesses physical properties more similar to cerium and praseodymium than europium. At temperatures above 20 degrees Celsius, it is the most paramagnetic element on the periodic table. An oxidized form of the element can be found in nature. Gadolinium was first discovered by Swiss chemist Jean Charles de Marignac in 1880 and was later isolated by Boisbaudran. At high temperatures, gadolinium forms binary compounds with many nonmetals. It also serves as a strong reducing agent in laboratory experiments. The only known industrial use of gadolinium is as shielding withing nuclear reactors.
Terbium – Element 65
Terbium has similar physical properties to europium. It is also exclusively found in minerals such as cerite, monazite, and euxenite. Terbium was discovered by Swedish chemist Carl Gustaf Mosander in 1843. Terbium is an electropositive element that reacts with water, halogens, and strong acids. One use of Terbium in industry is as a stabilizer in high-temperature fuel cells. It is also used in the production of electronic devices, such as sonar systems, and color TV tubes.
Dysprosium – Element 66
Dysprosium is a highly magnetic lanthanide. Its characteristic magnetic properties are made strongest when temperatures are very low. It is the slowest tarnishing lanthanide. Boisbaudran remarked on how difficult the element was to isolate with acids, subsequently naming it after the Greek word “dysprositos” translating to “hard to obtain”. The main application of dysprosium is magnets in wind turbines.
Holmium – Element 67
Holmium is a lanthanide that was discovered by Swedish chemist Per Teodor Cleve in 1878 via isolation. It is too reactive to occur in nature, however it is relatively stable in very dry conditions at room temperature. It is mined from minerals using a technique known as ion-exchange. Like many other lanthanides, holmium is strongly magnetic. It also has the relatively unique ability to absorb large quantities of neutrons, making it a very practical material to include in the construction of nuclear reactors.
Erbium – Element 68
Erbium is a silvery-white lanthanide originally found in Ytterby, Sweden, hence its name. The Er3+ ion gives off a fluorescent pink color, which is readily absorbed by water in biological tissue. This makes erbium well-suited to be used in surgical lasers. Other uses include metallurgy as it forms strong bonds with metals in the fourth row of the periodic table.
Thulium – Element 69
Thulium is a silvery-gray lanthanide which was also discovered by Per Teodor Cleve. It is the second rarest lanthanide after promethium. At very high temperatures, thulium functions as a superconductor. It is also used as a source of radiation in small X-ray devices. Thulium-170 is currently being researched as a radiation source for cancer treatment.
Ytterbium – Element 70
Ytterbium is a silvery-yellow metal that serves as the penultimate lanthanide. Like the other late lanthanides, ytterbium is capable of forming complexes with nine water molecules when placed in an aqueous solution. Many properties, such as melting point and boiling point, differ significantly from other lanthanides due to its closed-shell electron configuration. Ytterbium has a wide array of applications, from nuclear medicine to metallurgy to the construction of atomic clocks.
Conclusion on the Rare Earth Elements
Lanthanides are metallic elements that occupy positions 57-70 on the periodic table. When viewing the periodic table, they lie below the transition metals, and above the actinides.
Often referred to as the rare-earth elements, they all share some common physical characteristics such as color and malleability. However, some chemical properties differ between neighboring lanthanides. Their wide range of atypical properties are what make lanthanides such an important part of our modern technological world!