Lanthanum is a chemical element of the periodic system of Mendeleev. Its name comes from the Latin Lanthanum, translated from the Greek "lantano" - secrecy. Lanthanum is a rare earth metal. Its atomic number is 57, and its atomic mass is 138.9050. In nature, an element consists of two isotopes - lanthanum 139 and radioactive lanthanum 138.
Brief atomic and chemical characteristics
In the periodic table are in group III B, the sixth period. Nearby are cerium, neodymium.
The electronic formula of lanthanum: KLMN4s 2 4p 6 4d 10 5s 2 5p 6 5d 1 6s 2 , E ion (Me => Me + + e) = 5.59 eV. The atomic mass is 138.9055, the atomic radius is 187 pm, the density is 6.162 grams per centimeter cubic. The crystal lattice is hexagonal. Her period is 3,750 A.
The atom of the chemical element of lanthanum is a positively charged nucleus (+57), 57 protons and 82 neutrons are contained inside. Around the nucleus in 6 orbits, 57 electrons are in motion.
Detailed information on lanthanum is available in chemistry textbooks and is briefly described in this article.
A multiple history of the discovery of lanthanum
After the existence of the chemical element of lanthanum was theoretically predicted, they could not be found for 36 years. The pioneer of this metal should include the young Swedish chemist Jens Jakob Berzelius, who in 1803 carefully studied the mineral, which has now become known as cerite. The scientist determined that his structure is heterogeneous and contains some unknown element.
Somewhat earlier, a student chemist by the name of Erdman in the rocks of Norway discovered a mineral unknown to science, which he named Mozander in honor of his teacher Karl Mozander.
After some time, Mozander once again studied in detail the minerals found and concluded that, indeed, they contain a metal unknown to science. He was lucky to prove this only in 1839. As a result of his experiments, he identified a new element, which Berzelius proposed to call lanthanum.
Chemical properties, appearance
Lanthanum is soft, malleable. The metal is viscous. The chemical properties are ordinary, while it is highly refractory. Lanthanum is a silver-white metal. When in dry air, they protect their internal structure with an oxide film without oxidizing. However, if there is even a slight humidity in the air, then metallic lanthanum oxidizes quite quickly, turning into hydroxide.
When this metal is heated to a temperature of 400 degrees Celsius in an oxygen environment, it burns out. The flame is bright with a lot of heat. When glowing lanthanum in a nitrogen atmosphere forms a black nitride. In a chlorine medium, it ignites at room temperature. It is well dissolved in mineral acids. Does not respond to alkaline solutions. Compounds of the chemical element of lanthanum have a valency of 3+.
Upon contact with hydrogen, the metal begins to emit a large amount of heat even at an ambient temperature of about 20-25 degrees Celsius. It forms variable hydrides, since lanthanum differs in different degrees of hydrogen absorption, which depend on temperature.
Getting
Initially, lanthanum was obtained not in its pure form, but with a large amount of impurities. Mozander obtained this chemical element in the process of heating lanthanum chloride and potassium.
Currently, the industry is able to produce lanthanum with a purity of about 100%.
The chemical element lanthanum is isolated through a long and complex chemical process, which is associated with the separation of the feedstock into fractions. Lanthanum is always found in rocks with neodymium, cerium, praseodymium. Initially, cerium is isolated from such rocks, and then other chemical elements during ion chromatography and extraction. It is then separated by precipitation as lanthanum oxalate and calcined. The result is lanthanum oxide.
As a metal, lanthanum is obtained by treating compounds containing a large amount of lanthanum with calcium or electrolysis in combination with certain chemical catalysts.
Currently, in order to obtain metal on an industrial scale of high purity, up to 99.9%, more advanced extraction and ion-exchange methods are used. Lanthanum separation technologies are described in detail in specialized textbooks on chemistry.
Being in nature
In the earth's crust, the chemical element lanthanum is a rare material; it is not in vain that it is referred to as the so-called rare-earth elements. In nature, it does not exist in its pure form, it is a part of minerals, namely: bastenzite, monocyte, lopartite, apatite. This is a very scattered element. The content in the earth's crust is 1.8 . 10 -3 % of the total mass of the planet.
Lanthanide family
The chemical element lanthanum passed its name to the group in which 15 metals are combined. They are not like the rest of the elements. Their common name is lanthanides. They are also distinguished by the fact that to date they have been little studied, although they are used quite actively in industry.
Currently, interest in lanthanides is very high. It significantly increased after the first nuclear reactors began to work. They, including, as by-products form elements of the lanthanide group.
All representatives of the metals of the lanthanide group possess stable isotopes, with the exception of promethium. In total, the following metals belong to this series (group) of rare-earth elements:
- Lanthanum.
- Gadolinium.
- Holmium.
- Dysprosium.
- Europium.
- Ytterbium.
- Lutetium.
- Praseodymium.
- Promethium.
- Samarium.
- Terbium.
- Thulium.
- Cerium.
- Erbium.
Lanthanum Applications
Despite the fact that the metals of the lanthanide group are very few in the earth's crust, they are widely used in industry.
From materials containing lanthanum, wheels of extremely popular and sought-after lighters are made.
So, lanthanum oxide is used for the manufacture of optical glasses (the so-called lanthanum glass). Lenses, prisms made using this metal are used in photo and film equipment, in astronomical optics.
Lanthanum chromite, which is doped with magnesium, strontium or calcium, is used in the manufacture of reliable and high-temperature heaters capable of operating at temperatures up to 1780 degrees Celsius in an oxygen atmosphere. With increasing temperature, the resistance of lanthanum chromite decreases. The coefficient of thermal expansion of the chemical element of lanthanum is quite low, as a result of this, electric heaters are characterized by significant durability.
Lanthanum oxides are used in the synthesis of superconductors that are designed to operate at high temperatures.
The chemical element lanthanum found its application in the manufacture of special glasses intended for glazing rooms. Such canvases, the structure of which includes lanthanum compounds, have unique properties, they are able to reduce the temperature in the rooms to 7 degrees.
Lanthanum-nickel alloys (hydrides) are widely used as hydrogen accumulators. They are capacious and reliable storage. The prospect of being widely used in the automotive industry as containers for storing alternative fuel is open for them.
In electronics, lanthanum is used as a conductor. Lanthanum hexaboride has found its application in electron microscopes, this has significantly increased the resolution of electronic microscope systems, increase their resource.
As another prospect for the use of the chemical element of lanthanum, modern researchers see it as the main component of a new type of battery with solid electrolyte. Experiments show that such sources have a high specific electric capacity. They have a long life without energy loss. Differ in durability and durability. As a result, they may in the near future seriously compete with other batteries.
In medicine, preparations containing lanthanum have found application in hyperphosphatemia. They are prescribed as a drug that interferes with the absorption of phosphates during meals.
Lanthanum in the nuclear industry
High purity metallic lanthanum is very important in the nuclear industry. This chemical element is indispensable in the technology of processing nuclear fuel to produce plutonium. Molten lanthanum is poured into molten uranium, in which metallic plutonium is included as impurities. He immediately begins to extract plutonium isotopes from uranium, gradually floating up. It starts to float on the surface. It does not mix with uranium. The resulting alloy is then processed by chemical methods to extract plutonium. As a result, nuclear physicists claim that lanthanum is the father of nuclear weapons.