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# Rare Earth Minerals

Today we have a tabular arrangement of all known element which is known as Modern Periodic Table. This table is based on the increasing order of atomic number of elements. The basic of Modern Periodic table is that the physical and chemical properties of elements are periodic function of their atomic number. Initially few elements were known which were classified as metals and non-metals. After the discovery some more elements, this classification was not enough for all the elements. The need of a proper classification finally gave the Modern Periodic Table.

The Modern Periodic table consists of 18 groups and 7 periods. Here groups are vertical columns and periods are horizontal rows in the table. Group-1 is made up of Alkali metals which are highly reactive metals with $ns^1$ valance shell configuration. Next group is of Alkaline Earth Metals which are metals with $ns^2$ valence shell electronic configuration. From Group-3 to Group-12 are transition metals which are well known for their variable oxidation states. They are also called as d-block elements because their valence electrons are located in the d-orbitals. From Group-13 to Group-18 are part of p-block which contains metals, non-metals and metalloids. Apart from the main body of the Modern Periodic table, there are two series of 14 elements at the bottom of the main body of Periodic table. These two series of elements are called as f-block elements. First series of f-block elements is called as Lanthanides and second series is called as Actinides. These elements are found in very less amount therefore they are known as rare earth elements.

## What are Rare Earth Minerals?

Rare earth minerals are mainly Lanthanides with two d-block elements; Yttrium and Scandium. They are naturally occurring non-toxic minerals whose unique properties make them essential part of various technologies. They have almost same chemical and physical properties. The ability of discharge and accept electrons make them useful in many electronic, optical, magnetic equipments. Here ‘Rare’ word is not related to their abundance but express their unique chemical and physical properties. Only Thulium and lutetium are the least abundant elements in Earth crust. These elements are usually not found as free metals in the earth's crust but in the form of minerals and also as mixture with other elements. Rare earth elements can be classified as Light rare earth elements and Heavy rare earth elements. There are 5 light rare earth elements and 11 heavy rare earth elements including Yttrium.

## Rare Earth Minerals List

Rare earth elements (REE) or metals is a as a collection of 17 chemical elements in the periodic table; 15 lanthanides, Scandium and Yttrium. Scandium and yttrium are d-block elements but also a part of rare earth elements because they usually found in the same ore deposits as the lanthanides and also shows similar chemical properties. The classification of Rare Earth elements is on the basis of their electronic configurations. Light-group rare earth element (LREE) are from lanthanum (Atomic number-57) to gadolinium (Atomic number-64). These elements have unpaired electrons from 0 to 7. On the contrary, heavy rare earth elements start from Terbium (Atomic number-65) to Lutetium (Atomic number-71) with Yttrium (Atomic number-39). All of the heavy rare earth elements (HREE) have paired electrons. Yttrium and HREE have similar ionic radius and also chemical properties. Unlike Yttrium Scandium does not exhibit similar properties therefore is not a part of LREE and HREE. List of REE are given below;

 Lanthanide Series Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Scandium Yttrium

## Why Rare Earth Elements are Called Rare?

Unlike their name, Rare earth elements are relatively plentiful in the Earth's crust which is similar in crustal concentration to industrial metals like Cr, Ni, Cu, Pb etc. The term rare can be related to very little tendency to become concentrated in exploitable ore deposits. China and the United States have largest rare earth metal deposits in the form of bastnäsite and monazite. Mountain Pass in California, United States is also a dominant source of these elements. Because of similar chemical and physical properties, these elements cannot separate with simple separation methods but require special separation techniques.