Rare Earth Elements

Rare Earth elements are often termed as rare Earth metals. They comprise all those elements which are positioned in those two periods (or rows) that are detached from the main body of the periodic table. Basically, rare Earth elements got its name because there was a time when it was a very difficult task to purify these metals from their oxides. However, since 1945, easier methods like ion-exchange and solvent extraction processes have been used to obtain these elements in a pure form at a low cost.

Most of the rare Earth elements are present in the same minerals together in nature. The characteristics of these elements are so similar that sometimes it becomes difficult to differentiate them from one another. There are slight variations in solubility and complex formation which are utilized to separate the elements from each other. In the periodic table, the rare Earth elements belong to group 3 and the sixth and seventh periods. They are divided into two blocks. One is the lanthanide series and the other is the actinide series. Properties of rare Earth elements are very similar to that of transition metals. Hence, they are often said to be special transition metals.

Lanthanide Series of Rare Earth Elements

The position of lanthanides is the block 5d of the periodic table. The first element of this series is lanthanum. Metals of lanthanides are soft but metals with higher atomic numbers show some hardness. At room temperature, lanthanides burns in air, and in case the temperature is higher, rare metals of this series burn vigorously. In general, rare Earth elements of the lanthanide series adhere to water. When they react with water, hydrogen gas is released. They readily react with dilute acids at room temperature and give out hydrogen. On reaction with hydrogen, large amount of heat is released by the lanthanides. They possess strong reducing properties. Most of the compounds formed by rare elements of lanthanides are ionic. When heated with nonmetals, lanthanides form binaries.

Actinide Series of Rare Earth Elements

Rare Earth elements of the actinide series have individual distinctive structures. All the elements of the actinide series possess radioactive substances. A large number of allotropes of these metals are found. Electrons are present in the f-orbits in these elements. They are electropositive elements and tends to donate the electrons present in the outermost orbits. Metals of actinide series have high density. Actinides readily reacts with most of the non-metallic elements. On reaction with boiling water, actinides give out hydrogen gas.

Common Properties of Lanthanides and Actinides

Some of the properties of rare Earth elements are common in both the lanthanide as well as actinide series. In the pure form, they are highly lustrous substances, but when exposed to air they tends to get tarnished very easily. Colors of rare Earth elements vary in between silver, silvery-white or gray. All of them are good conductors of electricity.

Uses of Rare Earth Elements

Rare Earth elements of lanthanides have a number of scientific as well as industrial uses. Compounds of lanthanides plays the role of catalysts during the production of petroleum and many synthetic products. Lasers, some types of lamps, magnets, motion picture projectors, X-ray screens, etc., use rare Earth elements from the lanthanide series. Elements of actinides are used in nuclear fission.

Actually, in the lanthanide series, those elements which are followed by the element lanthanum, and in the actinide series, elements that come after actinium are rare Earth elements. That is why chemists often argue that the names of the elements lanthanum and actinium should be removed from the group of rare Earth elements.