Helium, neon, argon, krypton, xenon, radon, these six rare gases, the main role of those?

Rare gas monomers at room temperature for the gas, and in addition to argon, the rest of the several kinds of atmospheric content is very small (especially helium), so the name "rare gases", rare gases have historically been called "noble gases", this is because of their atom most This is because the outermost electron configuration of their atoms is 1s2 (superscript), except for helium, the rest are 8-electron configuration (ns2np6, both superscript), and these two configurations are stable structures. Therefore, the chemical properties of rare gases is very inactive, so in the past people have thought that they and other elements will not occur between chemical reactions, called "noble gases". However, it is this absolute concept has bound people's thinking, hindering the study of rare gas compounds. 1962, working in Canada, 26-year-old British young chemist N. Bartlett synthesized the first rare gas compounds Xe [PtF6] (6 for the subscripts), aroused a great deal of interest in the chemical community and attention. Many chemists competed to carry out this work, successively synthesized a variety of "rare gas compounds", promoting the development of rare gas chemistry. And the "noble gas" a also no longer accord with the facts, so renamed rare gases.

Physical and chemical properties of rare gases

Air contains about 1% (volume percent) of rare gases, most of which are argon. Rare gases are colorless, odorless, tasteless, slightly soluble in water, solubility increases with the molecular weight. The molecules of rare gases are composed of single atoms, their melting and boiling points are very low, with the increase of atomic weight, melting point and boiling point increase. They can all liquefy at low temperatures. The outermost electronic structure of the rare gas atom is ns2np6 (helium is 1s2), which is the most stable structure, therefore, it does not act with other elements under usual conditions, and has long been regarded as an inert element that is chemically very inactive and cannot form compounds. Until 1962, the British chemist N. Balliett only used the strong oxidizer PtF6 and xenon role, produced the first noble gas compounds Xe [PtF6], and later synthesized other noble gas compounds one after another, and its name changed to rare gases.

Air is the main raw material for the production of rare gases, and the rare gas mixture can be obtained through the graded distillation of liquid air, and then the low-temperature selective adsorption method with activated carbon can be used to separate the rare gases.

Helium is the lightest gas except for hydrogen, and can be used instead of hydrogen in spaceships without catching fire or exploding.

Liquid helium has a boiling point of -269°C. Ultra-low temperatures close to absolute zero (-273.15°C) can be obtained using liquid helium. Helium is also used to replace nitrogen as artificial air for sea divers to breathe, because more nitrogen will be dissolved in the blood when breathing with ordinary air in the deep sea where the pressure is higher. When the diver rises from the deep sea and the body gradually returns to normal pressure, the nitrogen dissolved in the blood will be released to form air bubbles, which will block the microvessels and cause "air congestion". The solubility of helium in the blood is much smaller than that of nitrogen, and by replacing ordinary air with a mixture of helium and oxygen (artificial air), the above phenomenon will not occur.

Argon is ionized by high-energy cosmic rays. Using this principle, a counter filled with argon can be set up in an artificial Earth satellite. When the satellite is flying in cosmic space, the argon gas is irradiated by cosmic rays. The stronger the irradiation, the stronger the ionization of argon. Satellite on the radio machine to these ionization signals automatically sent back to Earth, people can be based on the size of the signal to determine the location of the cosmic radiation belt in space and intensity.

Krypton absorbs X-rays and is used as a shielding material for X-ray work.

Xenon lamps also have a high level of ultraviolet radiation, which can be used in medical technology. Xenon can dissolve in the lipids of the cytoplasm, causing anesthesia and swelling of the cells, thus temporarily stopping the action of the nerve endings. A gas mixture of 80% xenon and 20% oxygen has been tried as an anesthetic without side effects. In the atomic energy industry, xenon can be used to test the presence of high-speed particles, particles, mesons, etc.

Radon is the only natural radioactive gas in nature, radon in the role of the human body at the same time will soon decay into the human body can be absorbed by the radon daughters, into the human respiratory system caused by radiation damage, induced lung cancer. In vitro radiation mainly refers to the natural stone in the radioactive body directly irradiated by the human body to produce a biological effect, will cause damage to the human body's hematopoietic organs, nervous system, reproductive system and digestive system.

However, radon also has its uses, beryllium powder and radon sealed in the tube, radon decay alpha particles released with the beryllium nucleus nuclear reaction, the neutrons produced can be used as a laboratory neutron source. Radon can also be used as a gas tracer for detecting pipe leaks and studying gas movement.

As an anesthetic, xenon is valued in medicine. Xenon can dissolve in the grease of the cytoplasm, causing anesthesia and swelling of the cells, thus temporarily stopping the action of the nerve endings. A gas mixture consisting of 80% xenon and 20% oxygen has been tried as an anesthetic without side effects.

Helium is the lightest gas besides hydrogen and can be used instead of hydrogen in spaceships without catching fire or exploding.

Liquid helium has a boiling point of -269°C. Ultra-low temperatures close to absolute zero (-273.15°C) can be obtained using liquid helium. Helium is also used to replace nitrogen as artificial air for sea divers to breathe, because more nitrogen will be dissolved in the blood when breathing with ordinary air in the deep sea where the pressure is higher. When the diver rises from the deep sea, the body gradually restores the normal pressure, the nitrogen dissolved in the blood should be released to form bubbles, which will block the microvessels and cause "air congestion". The solubility of helium in the blood is much smaller than that of nitrogen, and the use of a mixture of helium and oxygen (man-made air) instead of ordinary air will not cause the above phenomenon.

With the development of industrial production and science and technology, rare gases are more and more widely used in industry, medicine, cutting-edge science and technology, and even daily life.

The use of rare gases is extremely inactive chemical properties, some production sectors commonly used them as a protective gas. For example, in the welding of precision parts or magnesium, aluminum and other active metals, as well as the manufacture of semiconductor transistors in the process, commonly used as a protective gas argon. Atomic energy reactor nuclear fuel plutonium, in the air will also rapidly oxidize, also need to be protected by argon under mechanical processing. Electric light bulbs filled with argon can reduce the gasification of tungsten filament and prevent tungsten oxidation, in order to extend the service life of the bulb.

The rare gases emit light when energized. The world's first neon lamp is filled with neon gas made (neon lamp in English means "neon"). The red light emitted by neon lamps is highly transmissive in the air and can pass through dense fog. Therefore, neon lamps are often used in airports, harbors, land and water transportation lines on the lights. Lamps filled with argon or helium, respectively, when energized to emit light blue or light red light. Some lamps are filled with neon, argon, helium, mercury vapor and other four gases (there are three or two) of the mixture. Due to the relative content of various gases do not serve, they produce a variety of colorful neon lights. People commonly used fluorescent lamps, is filled with a small amount of mercury and argon in the tube, and in the inner wall coated with fluorescent substances (such as calcium halophosphate) and made. When energized, the tube due to mercury vapor discharge and produce ultraviolet light, fluorescent material, so that it emits a visible light similar to daylight, so it is also called fluorescent lamps.

Helium is the lightest gas other than hydrogen, and can be used instead of hydrogen in spaceships or balloons without catching fire or exploding.

Helium is also used to replace nitrogen as artificial air for sea divers to breathe. Sea divers can not use ordinary air to breathe, because the pressure increases, the solubility of the gas also increases, so in the pressure of the deep sea with ordinary air breathing, there will be more nitrogen dissolved in the blood. When the diver rises and the normal pressure is gradually restored, the nitrogen dissolved in the blood will be released, forming bubbles that will block the microvessels and cause "gas congestion". The solubility of helium in blood is much smaller than that of nitrogen, and the use of helium and oxygen gas mixture (artificial air) instead of ordinary air, the above phenomenon will not occur.

Liquid helium can be used to obtain temperatures close to absolute zero (-273.15°C).

Krypton absorbs X-rays and can be used as a shielding material for X-ray work.

Xenon also has a high level of ultraviolet radiation, which can be used in medical technology. Xenon can dissolve in the lipids of the cytoplasm, causing anesthesia and swelling of the cells, thus temporarily stopping the action of the nerve endings. A gas mixture consisting of 80% xenon and 20% oxygen has been tried as an anesthetic without side effects.

In the atomic energy industry, xenon can be used to test the existence of high-speed particles, particles, mesons, etc.