Cesium, element symbol Cs, atomic number 55, located in the sixth cycle, group IA, its elemental substance is a light golden yellow active metal with low melting point, which is easily oxidized in the air and can be generated by violent reaction with waterhydrogenAnd explode[1]。Cesium is not found in natureSimple substanceForm, only insaltIts form is rarely distributed on land and in the sea.Cesium is used to manufacture vacuum devicesPhotocellAnd other important materials.Radionuclide Cs-137 is one of the radioactive pollutants leaked from the Fukushima Daiichi Nuclear Power Station in Japan.
Cesium metal belongs to hazardous chemicals, which are flammable and self combustible when wet.Be careful when using[3]
chemical property
cesium
The biological behavior of cesium is similar to that of potassiumCesium-13724 hours later, cesium-137 can be fully absorbed by human body and combined in cells, causing internal radiation.[4]
Cesium-137 can be used as γ radiation source for radiation breeding, irradiation storage of food, sterilization of medical devices, cancer treatment and γ flaw detection of industrial equipment.Because of the long half-life of cesium source and its vulnerability to diffusion, cesium-137 source has gradually beenCobalt-60Source replaced.[3]
On March 29, 2011, extremely small amounts of artificial radionuclides cesium-137 andCesium-134, the concentration is 10-5Baker/m3 and below.Cesium-137 in the environment is easily absorbed after entering the human body and evenly distributed throughout the body;Because cesium-137 can releaseGamma ray, which can be easily measured in vitro.Radioactive cesium entering the body mainly remains in the soft tissues of the whole body, especially in the muscles, with low concentrations in bone and fat;A large amount of radioactive cesium ingested into the body can cause acute and chronic damage.[5]
Its radioactivity and brief characteristics
nuclide
Chemical symbol
Atomic number
Major radioisotopes
half life
source
toxicity
cesium
Cs
fifty-five
one hundred and thirty-sevenCs
30.0 years
artificial
poisoning[6]
Caesiumchemical propertyExtremely active, cesium generates a layer of grayish blue oxide in the air, which can spontaneously ignite in less than a minute, emitting a deep purple red flame, generating very complex cesium oxide.[2-3]
Cesium is the most active among alkali metals, which can react violently with oxygen to generate a variety of cesium oxides.In humid air, the heat of oxidation is enough to melt cesium and burn it.Cesium does not react with nitrogen, but can combine with hydrogenation at high temperature to produce fairly stablehydride。Cesium can react violently with water. If cesium is put into the water tank, it will explode immediately.It can even react violently with ice whose temperature is as low as - 116 ℃hydrogen、Cesium hydroxideThe cesium hydroxide generated is the most alkaline among the non radioactive hydroxides.AndhalogenIt can also generate stablehalide, which is due to itsIonic radiusThe characteristics brought by the big.Cesium and organics can also react similarly to other alkali metals, but they are more active.[2]
Caesium iodideAndBismuth triiodideThe reaction can generate insoluble bright red double salt, which is used for qualitative and quantitative determination of cesium;The flame of cesium is purple red darker than potassium, which can be used to detect cesium.[2-3]
Cesium salts are usually colorless unless anions are colored (e.gCesium permanganateIt's purple).Many simple salts are deliquescent, but weaker than lighter alkali metals.CaesiumAcetate、carbonate、halide、oxide、NitrateandsulfateSoluble in water.Double saltGenerally, the solubility of aluminum sulfate and cesium is small, which is often used to purify cesium from ores.And antimony (e.g. CsSbClfour）、bismuth、cadmium、copper、ironThe double salt formed with lead usually has low solubility.
Cesium can be usedElectrolytic methodAnd thermal reduction method.However, due to its strong corrosiveness to the electrode, electrolysis is generally not used in industry.So in industryCesium chlorideAt high temperature, cesium is produced by reduction of metallic calcium.[6]
application area
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Fission product
Long life cesium-137 is uranium-235Fission product。Half life 30.17 years, radiationBeta rayandGamma ray, used as β and γ radiation source, used in industry, agriculture and medical treatment.With the storage time of nuclear fuel radioactive waste, the proportion of its γ - ray radiation increases, which is the main object of storage.[4]
Ion rocket
In order to explore the universe, there must be a brand new and extremely fast means of transportation.Ordinary rockets and spaceships can not reach such a speed, and they can only rush out of the Earth Moon system at most;Only those that can fly more than 100000 kilometers per hour“Ion rocket”To meet the requirements.[3][5]
The outermost electron of cesium atom is extremely unstable, and it is easy to be excited and emitted to become a positively charged cesium ion, so it is an ideal "fuel" for ion rocket engines in space navigation.Working principle of cesium ion rocket: after the engine starts, a large amount of cesium vapor is generated. The cesium vapor is "processed" by the ionizer and becomes a positively charged cesium ion. Then it accelerates to 150 kilometers per second under the action of the magnetic field and is ejected from the nozzle. At the same time, it gives a strong impetus to the ion rocket and pushes the rocket forward.[3][5]
The calculation shows that the thrust per unit weight produced by using this cesium ion as the propellant of the space rocket is hundreds of times higher than the liquid or solid fuel used.This cesium ion rocket can travel in space for one or two years or even longer.[3][5]
atomic clock
The outermost electrons of the cesium atom surroundNucleusThe speed of rotation is always extremely accurate to complete a circle in a few billionths of a second, and the stability is much higher than the rotation of the earth on its axis.Using this feature of cesium atoms, people have made a new type of clock——Cesium atomic clockOne second is the time required for the cesium atom to "vibrate" 9192631770 times (that is, it is equivalent to 9192631770 transitions of two hyperfine electrons of the cesium atom).This is the latest definition of "second".[3][5]
With the cesium atomic clock, people can measure the time of one billionth of a second with great accuracy, which is far more accurate and stable than any kind of watch in the world before, and also exceeds the astronomical time that has been based on the rotation of the earth for many years.With clocks such as cesium atomic clocks, it is possible for human beings to engage in more sophisticated scientific research and production practices, such as the explosion of atomic bombs and hydrogen bombs, the launch of rockets and missiles, and space navigation. They can also be used for long-distance flight and navigation.The atomic clock made of cesium can accurately measure one billionth of a second. It has been running for 300000 years with an error of no more than 1s. Its accuracy is quite high.In addition, cesium is widely used in medicine, missiles, spaceships and various high-tech industries.[3][5][7]
New particle
February 2023,Australian scientists wrote in the latest issue of Physical Review Letters that they have improved their understanding of the magnetic structure of cesium nuclei, their role in cesium atoms and the muon effect through theoretical research by means of an unusual atom composed of an ordinary cesium atom and a basic particle called muon.The latest method is expected to provide a different way to discover new particles from the Large Hadron Collider, or help reveal the secret of dark matter, which accounts for 95% of the total mass of the universe.[9]
Cesium fountain clock
Cesium fountain clock is one of the most accurate clocks in the world.[10]
A brief history of discovery
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1.3611kg high purity metallic cesium produced in the Soviet Union
Cesium is finallyKirchhoffProfessor and Ben, born in 1860, were found in Heidelberg, Germany.They tested the mineral water from Durkheim, and observed lines in the spectrum that they could not recognize, which meant the emergence of a new element.They produced about 7g from this sourceCesium chloride, but failed to produce samples of this new metal itself.The honor of the first successful production of metallic cesium belongs to Professor Carl Theodor Setterberg of the University of Bonn, who is a professor ofCesium cyanide(CsCN) obtained it.[5]
It was named after its discoverer Professor Kirchhoff and my student in Latin "coesius" (meaning sky blue).[2][5]
Distribution of mineral resources
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Domestic metal cesium
Cesium content in the crust is 2 × 10-3%。Cesium garnet is a cesium bearing mineral, and it is also the main raw material for extracting cesium.34 kinds of cesium isotopes have been found, of which cesium-133 is the only stable isotope existing in nature, and the rest are produced by uranium fissionradio isotope。[4]
The mineral water of Durkheim contains rich cesium compounds, so it is possible to extract metallic cesium from the mineral water of Durkheim.[2]
Cesium is generally distributed in water with more minerals.[2]
