Rare earths - a relatively small group of elements, which has a total of 17 representatives.All these substances are presented a silver-white color.
rare earth elements and the history of their discovery
This group of substances has been opened recently.Samples were first discovered in 1794.While the Finnish chemist Johan Gadolin investigated samples of ore near the village called ytterbium.Here he found unknown "liquid earth", which was then named after the location - yttrium.After some time, the samples examined again Klaport Martin, which has allocated an additional substance, named after a planet Ceres cerium.
But by 1907 it was found to have 14 such elements.
So the name "rare earth metals" was introduced in the late 18th century.Here, the role played by the fact that all the elements of the groups form refractory oxides that are practically insoluble in water.In addition, scientists at the time mistakenly believed that these metals are rare in the earth's crust.
Rare earth metals: the representatives of the group
As already mentioned, this group consists of 17 chemical elements.These include:
- Lanthanum.
- Cerium (named after a planet Ceres).
- Neodymium.
- Pradeozim.
- Samaria.
- promethium.
- Gadolinium.
- Europe.
- Terbium.
- Holmium.
- Dysprosium.
- Erbium.
- Ytterbium.
- Lu.
- Thule.
Interestingly, the levels of these outer electrons of atoms are almost identical.This explains the chemical and physical properties of metals.
rare earth metals and their chemical properties
Representatives of this group have relatively high reactivity, which is especially high when heated.For example, at an elevated temperature, some metals are able to react with hydrogenous.
Furthermore, by heating these elements react with oxygen, forming a resistant, water-insoluble oxides.Incidentally, when burning metals in an oxygen atmosphere observed evolution of considerable heat.It is typical for this group pyrophoricity - property sparkle in the air.
Rare earth metals may also form hydroxides that are poorly soluble in water and some have amphoteric properties.
Almost all members of the group are characterized by the oxidation state +3.Active elements varies.The most active is considered to lanthanum.
mining of rare earth metals
In most cases, rare earth metals occur together.One rock sample contained several members of the group.To date, more than 250 known minerals, which are composed of rare earth elements.The main minerals include monazite Parise Księte, orthite.
most common substance in the earth's crust is considered cerium.But thulium and lutetium in nature contains the fewest.
In 2008, the world was mined about 124 thousand tons of rare-earth metals.The leaders in this production is considered to countries such as India, China and Brazil.
Another place of vast deposits of rare earth metals were discovered in 2011.These areas are located on the bottom of the Pacific Ocean near Hawaii, French Polynesia and Tahiti.
Rare earth metals and their application
These elements are used in very different industries.For example, they are widely used in the glass industry.Firstly, they increase the translucency of the glass.Secondly, these metals are used for the production of specialty glass - glass absorbs ultraviolet rays or infrared transmissive cure.With the help of rare earth materials produce heat-resistant glass.
in refining these elements act as catalysts.They are also used in the chemical industry for the production of high quality paints, varnishes and pigments.
