The use of rare gases
Rare gases are used to provide an inert atmosphere on many occasions. In chemical synthesis, argon is often used to protect compounds sensitive to nitrogen. Solid argon is also used to study very unstable compounds, such as reaction intermediates, by isolating them in a matrix composed of solid argon at ultra-low temperature. Helium is the carrier of color in gas chromatography and the filling gas of thermometer, which is used in Geiger counter, bubble chamber and other radiation measuring equipment. Helium and argon are used as shielding gases for welding arc, and inert shielding gases are used for welding and cutting base metal. They are also widely used in other metallurgical processes and silicon production in the semiconductor industry.
Some rare gases have direct medical uses, such as: helium is sometimes used to improve the breathing of asthma patients; Xenon is an anesthetic, because it has high solubility in lipids, is more effective than nitrous oxide (commonly known as nitrous oxide), and is easily discharged from the body, and wakes up faster after anesthesia. Xenon is used to take medical images of the lungs in hyperpolarized magnetic resonance imaging. Radon with strong radiation can only produce trace amounts, which can be used for radiotherapy.
Are rare gases pure?
Rare gas refers to inert gas. It is also called rare gas because of its low content in the crust and atmosphere. There are six kinds of inert gases, arranged in the order of increasing atomic weight, followed by helium, neon, argon, krypton, xenon and radon. Under normal circumstances, they do not combine with other elements, but only exist in the form of a single atom, which is pure.
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What is a rare gas?
Rare gas refers to the elemental gas corresponding to all the 0-group elements in the periodic table of elements, also known as inert gas. It is a colorless and odorless monoatomic gas at normal temperature and pressure, so it is difficult to carry out chemical reactions. There are seven kinds of rare gases * * *, namely helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn, radioactive) and (Ao) (Og, radioactive, artificial element). Among them, Og is a synthetic rare gas. Its nucleus is very unstable and its half-life is very short, only 5 milliseconds.
Main applications:
With the development of industrial production and science and technology, rare gases are more and more widely used in industry, medicine, cutting-edge technology and even daily life.
Using the extremely inert chemical properties of rare gases, some production departments often use them as protective gases. For example, argon is often used as a shielding gas in the process of welding precision parts or active metals such as magnesium and aluminum and manufacturing semiconductor transistors. Plutonium, the nuclear fuel of an atomic energy reactor, will also be oxidized rapidly in the air, and it also needs to be processed under the protection of argon. Argon gas filling in light bulb can reduce the gasification of tungsten wire and prevent the oxidation of tungsten wire, thus prolonging the service life of light bulb. Helium is the carrier of color in gas chromatography and the filling gas of thermometer, which is used in Geiger counter, bubble chamber and other radiation measuring equipment. Helium and argon are used as shielding gases for welding arc, and inert shielding gases are used for welding and cutting base metal. They are also widely used in other metallurgical processes and silicon production in the semiconductor industry.
Rare gases glow when electrified. The first neon lamp in the world was made of neon gas (the English original meaning of neon lamp is "neon lamp"). The red light emitted by neon lights has strong transmittance in the air and can pass through dense fog. Therefore, neon lights are often used in airports, ports and land and water transportation lines. The lamp tube is filled with argon or helium, which emits light blue or light red light when energized. Some lamps are filled with a mixture of four gases (three or two), such as neon, argon, helium and mercury vapor. Because the relative contents of various gases are different, colorful neon lights are made. The fluorescent lamp commonly used by people is made by filling a small amount of mercury and argon into the lamp tube and coating the inner wall with fluorescent substances (such as calcium halophosphate). When electrified, the lamp tube produces ultraviolet rays due to mercury vapor discharge, which excites fluorescent substances and makes them emit visible light similar to sunlight, so it is also called fluorescent lamp. Krypton can reduce the evaporation rate of filament, which is often used in incandescent lamps with high color temperature and efficiency, especially in halogen lamps. Krypton can be mixed with a small amount of iodine or bromine compounds. Xenon is usually used in xenon arc lamps because their continuous spectrum is similar to sunlight. This kind of lamp can be used in movie projectors and car headlights.
Rare gases can be made into various mixed gas lasers. He-Ne laser is one of them. He-Ne mixed gas is sealed in a special quartz tube. Excited by an external high-frequency oscillator, inelastic collisions occur between atoms of the mixed gas, and energy transfer occurs between excited atoms, thus generating electronic transitions and emitting stimulated radiation waves and near-infrared light corresponding to the transitions. He-Ne laser can be used for measurement and communication. Rare gases can be used in excimer lasers because they can form short-lived excitons. These excitons used in the laser can be rare gas dimers, such as Ar2, Kr2 or Xe2, and are more likely to be excitons combined with halogen, such as ArF, KrF, XeF or XeCl. The ultraviolet wavelength generated by these lasers is shorter. The ultraviolet wavelength generated by ArF is 193nm, while the ultraviolet wavelength generated by KrF is 248nm. This high-frequency laser makes high-precision imaging a reality. Excimer laser has many applications in industry, medicine and science. Excimer laser must be used in microlithography and microfabrication in integrated circuit manufacturing. Laser surgery, such as vascular remodeling and ophthalmic surgery, also needs excimer laser.
Helium is the lightest gas except hydrogen, which can be installed on the airship instead of hydrogen and will not catch fire and explode. The boiling point of liquid helium is -269℃, which is the most difficult to liquefy among all gases. The ultra-low temperature (-273.438+05℃) near absolute zero can be obtained by using liquid helium. Helium is also used to replace nitrogen as artificial air for sea divers to breathe, because in the high-pressure deep sea, more nitrogen will be dissolved in the blood when breathing with ordinary air. When the diver rises from the deep sea and gradually returns to normal pressure, the dissolved nitrogen in the blood will be released to form bubbles, which will block the capillaries and cause "air blockage". The solubility of helium in blood is much less than that of nitrogen. If helium-oxygen mixture (artificial air) is used instead of ordinary air, the above phenomenon will not happen. Liquid helium with a temperature above 2.2K is a normal liquid, which has the commonness of general liquid. Liquid helium with a temperature below 2.2K is a superfluid with many abnormal properties. Such as superconductivity, low viscosity, etc. Its viscosity becomes 1% of that of hydrogen, and this liquid helium can flow upward along the inner wall of the container and then slowly flow downward along the outer wall of the container. This phenomenon is of great significance for studying and verifying quantum theory.
Argon will ionize when irradiated by high-energy cosmic rays. Using this principle, a counter filled with argon can be installed on the artificial earth satellite. When a satellite flies in space, argon will be irradiated by cosmic rays. The stronger the radiation, the stronger the ionization of argon. The radio on the satellite will automatically send these ionization signals back to the earth, so people can judge the position and intensity of the cosmic radiation belt in space according to the size of the signals.
Krypton can absorb X-rays and can be used as a shading material when X-rays work.
Xenon lamp also has a high degree of ultraviolet radiation, which can be used in medical technology. Xenon can dissolve in the lipid of cytoplasm, causing anesthesia and expansion of cells, thus temporarily stopping nerve endings. People have tried to use a mixture of 80% xenon and 20% oxygen as an anesthetic without side effects. Xenon can be used to test the existence of high-speed particles, particles and mesons in the atomic energy industry.
Isotopes of krypton and xenon are also used to measure cerebral blood flow.
Radon is the only natural radioactive gas in nature. After radon acts on the human body, it will quickly decay into radon daughters, which will be absorbed by the human body and enter the human respiratory system, causing radiation damage and inducing lung cancer. Thorium impurities in general inferior decoration materials will decay and release radon gas, which will cause harm to human body. External radiation mainly refers to a biological effect produced by the radiator in natural stone directly irradiating human body, which will cause damage to hematopoietic organs, nervous system, reproductive system and digestive system in human body. However, radon also has its uses. Beryllium powder and radon are sealed in a tube. Alpha particles released during radon decay react with beryllium nucleus, and the generated neutrons can be used as neutron sources in the laboratory. Radon can also be used as a gas tracer to detect pipeline leakage and study gas movement.