175.0This page contains brief profiles and pictures of each of the Lanthanide metals. More information can be found via the WWW links following each element. However, as these links are to other servers on the Internet you will need to use the BACK button on your browser to return to this page. Credits for the photos and principal links can be found at the end of this document.
Discovered by Berzelius and Hisinger in 1803, but not isolated as a metal until 1875, cerium (named for the asteroid Ceres) is the most abundant of the so-called rare-earth metals. It begins the series of lanthanides that runs from elements 58 to 71. In pure form the element is a malleable and ductile metal, similar in coloring to iron. It is much more reactive than iron, however, readily oxidizing in moist air and releasing hydrogen from boiling water. Friction from abrading a sample can cause it to ignite.
Although the metal itself is too reactive for most uses, compounds of cerium are used in glass making and photography. It has limited use in some special alloys as well. Most commercial grade cerium is derived from monazite sand which is a mixture of phosphates of many of the rare earth metals along with calcium and thorium.More background information on Ce More data on Ce
Praseodymium, which is named from the Greek prasios + didymos (green twin), was isolated and identified by von Welsbach in 1885 from what was known at the time as didymium. von Welsbach's work revealed that this "substance" actually contained two new elements, one of which was praseodymium (neodymium was the other).
Pure praseodymium is silvery-white and fairly soft. It oxidizes slowly in air and reacts vigorously with water to release hydrogen gas. It is used as an alloying agent along with magnesium for parts in aircraft engines. Misch metal is 5% praseodymium and is used for alloying steel and in flints used to create sparks in lighters. The glass in welder's goggles contains a mixture of praseodymium and neodymium.More background information on Pr More data on Pr
Discovered in 1885 along with praseodymium, neodymium is named from the Greek neos + didymos (new twin). The silvery-white metal oxidizes easily in air and reacts with water, displacing hydrogen gas. Although another of the "rare" earth metals, neodymium is actually more abundant than many better known metals such as gold, silver, tin and lead.
Misch metal, used in lighter flints, is about 18% neodymium. The element is also used in the manufacture of artificial rubies for laser applications.More background information on Nd More data on Nd
The existence of promethium (for the Greek god, Promethius) was predicted in 1912 when Henry Moseley developed an x-ray method for determining integer atomic numbers of elements. An element was clearly missing between neodymium and samarium. It's existence was not confirmed until 1947 by Marinsky, Glendenin and Coryell.
Historical claims for the discovery of element 61 create an interesting trail from around 1925 in Florence (suggested name: florentium) to America in 1926 (suggested name: illinium). None of the claims, however, could be substantiated and today we know they were not simply a result of fleetingly small samples but rather poor work.
While spectral lines of promethium are evident in the light from some stars, it now seems apparent that no promethium is found in accessible areas of the earth--hence the difficulty in finding any! Initial attempts at synthesis of element 61 in a cyclotron at Ohio State University in 1941 led to the suggested name cyclonium. But the recognized synthesis and identification finally came at Oak Ridge in 1947.
The longest-lived isotope of promethium is Pm-145 with a half-life of 17.7 years. There are no significant commercial uses of the metal and so very little has been produced except for theoretical studies.More background information on Pm More data on Pm
Named for the mineral samarskite from which it is extracted, samarium was isolated and identified by de Boisbaudran is 1879. The pure metal has a silver lustre and tarnishes slowly at room conditions. It is readily magnetized and holds its magnetism extremely well. Rare earth magnets (samarium-cobalt, for example) exploit this property.
Although it is present in samarskite, commercial production of samarium is from monazite sand which can contain as much as 2.8% Sm by weight.
The symbol for samarium also happens to be my initials!More background information on Sm More data on Sm
Europium looks and feels a lot like lead, although it is not as dense. It was discovered in 1896 and isolated in 1901 by Demarcay, working with samples of supposedly "pure" samarium. Named for the continent of Europe, the element ranks thirteenth in abundance among the rare earth metals, but there is more of it than silver and gold combined.
It is the most reactive of the rare earth metals, behaving with water in a manner similar to calcium.
Generally refined from monazite sand, the pure metal has few applications, but you would find it less interesting to read this without some of its compounds which are used as activators and red phosphors in color CRT screens for television and computers.More background information on Eu More data on Eu
Gadolinium (from the mineral gadolinite, named for the Finnish chemist Gadolin) is a soft silvery-white metal that is used as an alloying agent in some steels and in the manufacture of some electronic components.
Credit for its discovery is shared by de Marignac who did extensive spectroscopic studies on the mixture then known as didymia, and by de Boisbaudran who finally isolated the metal in 1886.
The metal has a very large capacity for absorbing thermal neutrons, making it an excellent material for control rods in fission power plants.More background information on Gd More data on Gd
Terbium is fourteenth in abundance among the 17 metals usually counted as "rare-earths", present in the earth's crust to the extent of only 0.9 ppm (about 1 teaspoon in every 63 tons of earth). Named for the Swedish village of Ytterby, the metal was discovered in 1843 by Mosander (along with erbium).
Small amounts of terbium are used in special lasers and some solid state devices. The monazite sand from which terbium is generally extracted contains only about 0.03% by weight of Tb.More background information on Tb More data on Tb
The Greek word dysprositos (hard to get at) gives some indication of the scarcity of dysprosium, but only to a degree. It is about twice as abundant as uranium. The soft, silvery metal was discovered by de Boisbaudran in 1886 and it was finally isolated in 1906 by Urbain. A pure sample was not produced until the 1950s.
The pure metal oxidizes readily in air.More background information on Dy More data on Dy
Holmium was discovered by Cleve in 1879 and named for the Latinized version of the name for Stockholm. Like most of the other rare-earth metals, it is silvery and soft, and can be pounded or rolled into very thin sheets. At normal temperatures it is fairly inert but will oxidize at high temperatures and humidities.
Like most of the rare-earth metals, holmium is generally obtained from monazite sand, where it is present to the extent of about 0.05%. Most holmium use is confined to research.More background information on Ho More data on Ho
Like the histories of the discoveries of many other rare-earths, the tale of erbium reads like a series of mistaken identities. These elements are generally found as oxides and most often together. Chemically, the oxides are very similar and at the time of their first examination were difficult to separate. Thus a sample of "lanthanum" might end up containing two additional elements that no one had bothered to look for. Many chemists thought that the oxides were elements themselves at one time.
The oxide of yttrium (which along with scandium and lanthanum is generally included with the "rare-earths") known as yttria was eventually found to contain erbia and terbia as well, the oxides of, respectively, erbium and terbium. But the two are so similar that they were often confused in early work and what we now call erbium was originally terbium! In both cases, the credit for discovery goes to Mosander (1843 for erbium) and both elements were named for the Swedish town of Ytterby (which, by the way, also lends its name to Ytterbium and Yttrium----certainly some kind of record where naming elements is concerned!).
Like most of the rare-earth metals, erbium is silvery and soft, tarnishing slightly in air.More background information on Er More data on Er
The rarest of the naturally-occurring rare-earth metals, thulium was discovered in 1879 by Cleve, working from samples of erbia, an oxide of erbium. The metal is named for the ancient name for Scandinavia, Thule.
Like others in the lanthanide series, thulium is silver in color but it is also very soft---soft enough to cut with a knife.More background information on Tm More data on Tm
The first of the so-called "rare-earths" to be discovered, ytterbium takes its name from the Swedish village Ytterby (also the source of the names for terbium, erbium and yttrium). Discovery is credited to de Marignac in 1878. Initial identification was tediously made from the same mixture that most chemists of the time worked from: oxides of the lanthanides which gave rise to the term "rare-earth" due to its powdery consistency and often brownish color. But with the chemical separation techniques available at the time, it was very difficult to distinguish these similar elements. Even ytterbium itself turned out to hide another element. Lutetium was separated from it in 1907.
Pure ytterbium is like most of the lanthanides: silvery and ductile, reacting slowly with air to form an oxide. Mostly obtained from monazite sand, ytterbium makes up about 0.03% of that mixture.More background information on Yb More data on Yb
Lutetium ranks among the rare-earths in abundance only above thulium and promethium (and there's none of that anyway!). It official name comes from an ancient name for Paris, Lutecia, but it has had many names, most recently lutecium (only a change in official spelling). It was discovered independently by von Welsbach and Urbain in 1907-08.
The refinement of ion exchange methods and their application to the separation of the rare-earths made the separation of lutetium from ytterbium possible. von Welsbach decided to rename ytterbium aldebaranium and picked cassiopium for element 71. Urbain preferred neoytterbium and lutecium. Urbain's choices eventually were accepted, although the prefix was dropped from ytterbium and the spelling of lutecium was eventually changed.
The metal is the hardest and densest of the rare-earths and is the last of the lanthanides.More background information on Lu More data on Lu
Sources: Photos of the elements were taken from the LIFE Science Library book Matter. Background links go to the Periodic Table created at Los Alamos National Laboratories by Robert Husted. Data links go to the primary site of Mark Winter's WebElements, version 2.0, at the University of Sheffield in the United Kingdom.