A Noble Gases(Rare Gases) is a group 0 element on the periodic table. At normal temperature and pressure, they are colorless and odorless monoatomic gases, making it difficult to carry out chemical reactions.

There are seven kinds of rare gases, which are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), strontium (Rn, radioactive), gas (Og, radioactive, artificial elements). Among them, Og is a synthetic Noble Gas, the atomic nucleus is very unstable, and the half-life is very short only 5 milliseconds.

According to the periodic law of the element, it is estimated that Og is more active than radon. However, theoretical calculations show that it may be very lively. However, the carbon group cerium (Fl) exhibits properties similar to those of rare gases.

Noble Gas Definition

“Noble gases” have been renamed many times since they were discovered by chemists in the 19th century. Originally they were called noble gases (rare gases) because chemists think they are very rare.

However, this statement applies only to some of these elements, not all of which are rare.

Noble Gases

For example, argon (Ar, argon) accounts for 0.923% of the Earth’s atmosphere, which is better than carbon dioxide (0.03%). Helium (Helium) is rare in the Earth’s atmosphere, but it is quite abundant in the universe. It occupies 23%, second only to hydrogen (75%).

Therefore, chemists have changed to inert gases(also known as inert gases), indicating that their reactivity is very low, and no compounds have appeared in nature. For scientists who have to use compounds to find elements in the early days, these elements are hard to find.

However, recent research indicates that they can be combined with other elements into a compound (this is a rare gas compound), but only by means of artificial synthesis. Therefore, it was renamed as a noble gas (also known as a noble gas, noble gas or noble gas).

This name was translated by German-made Edelgas and was named by Hugo Edman in 1898. “Noble” is similar to ”precious metal” such as gold, indicating that they are not susceptible to chemical reactions, but are not capable of producing any compound.

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Noble Gas Discovery

In 1868, astronomers found a special yellow line D3 in the spectrum of the sun, which is different from the two yellow lines of D1 and D2 of the already known sodium element, suggesting that there may be an unknown element in the sun. This element was later named “helium”, meaning “the sun element”.

20 years later, Ramsey also confirmed the existence of the planet helium. In 1895, the American geologist Hillbrand observed that the uranium ore was heated in sulfuric acid to produce a gas that could not be self-igniting or combustible.

Noble Gases

He believes that this gas may be nitrogen or argon, but did not continue to study. Ramsey knew that after this experiment, the experiment was repeated with uranium ore and a small amount of gas was obtained.

When the gas was examined by spectroscopic analysis, it was thought that the line of argon could be seen, but a yellow line and several faint bright lines of other colors were unexpectedly found.

Ramsey contrasts it with known spectral lines, none of which is similar to it. After much thought, I finally remembered the embarrassment of the sun discovered 27 years ago.

The spectrum of helium is the yellow line. If the two yellow lines can overlap, the gas released from the uranium ore should be the sun element.

Ramsey was very cautious. At the time, Krux, the most famous spectroscopy expert in the UK, helped to verify that the unknown gas obtained by Ramsey was the “solar element” gas. In March 1895, Ramsey first published a briefing on the discovery of cockroaches on Earth in Chemical News.

In the same year, the discovery was officially announced at the British Chemical Conference. Later, people found cockroaches in the atmosphere, in water, in natural gas, in liquefied petroleum gas, in ores of uranium and beyond, and even in meteorites.

In 1902, Dmitry Mendeleev accepted the discovery of helium and argon, and these Noble gases were included in his elemental arrangement, classified as 0, and the periodic table evolved from this arrangement.

Ramsey continues to use fractional distillation to separate liquid air into different components to find other Noble gases. In 1898 he discovered three new elements: Krypton, neon, and xenon. “Krypton ” is derived from the Greek word “κρυπτ(kruptós)”, meaning “hidden”; “Neon” is derived from the Greek word “νο(néos)”, meaning “new”; “Xenon” is derived from the Greek word “ξνο ( Xénos)” means “stranger.”

Noble Gases

Helium was discovered by Friedrich Ernst in 1898 and was originally named radium radiation, but was not classified as a rare gas at the time. It was not discovered until 1904 that its properties were similar to those of other Noble gases. In 1904, Rayleigh and Ramsey won the Nobel Prize in Physics and Chemistry respectively for their discovery in the field of rare gases.

The President of the Royal Swedish Academy of Sciences, West Blom, said: “Even if the predecessors failed to confirm any of the elements of the family, they could still discover a new elemental family. This is unique in the history of chemistry and has an essence for scientific development. The special meaning of the above.

The discovery of Noble gases contributes to the development of a general understanding of atomic structure. In 1895, the French chemist Henry Movasan tried to react between fluorine (the most electronegative element) and argon (rare gas), but did not succeed.

Until the end of the 20th century, scientists were still unable to produce argon compounds, but these attempts helped to develop new atomic structure theory. From these experimental results, Danish physicist Niels Bohr proposed in 1913 that electrons in atoms are arranged in an electron layer around the nucleus, with the exception of the outermost layer of all rare gas elements except helium.

It contains 8 electrons. In 1916, Gilbert Newton Louis developed the octagonal rules, stating that eight electrons on the outermost electron layer are the most stable arrangement of an atom; this electronic arrangement prevents them from reacting with other elements. Because they don’t need more electrons to fill their outermost electron layer.

But by 1962, Neil Bartlett discovered the first rare gas compound, hexafluoroplatinate. Other rare gas compounds were subsequently discovered, and in 1962, the bismuth compound, bismuth difluoride was discovered. In 1963, the bismuth compound, bismuth difluoride, was discovered. In 2000, the first stable argon compound, hydrogen fluoride hydrogen hydride (HArF), was successfully prepared at 40K (-233.2 ° C).

Noble Gases

In December 1998, the Russian Dubna Joint Institute for Nuclear Research scientists bombarding plutonium with calcium atoms to produce 114 elements of a single atom, later named Fl. Preliminary chemical experiments have shown that this element may be the first superheavy element, although it is located in the 14th group of the periodic table, but has the rare gas characteristics.

In October 2006, the Joint Institute for Nuclear Research and the US Lawrence Lifestyle molar National Laboratory scientists successfully bombarded californium with calcium atom method of artificial synthesis of Og, which is the seventh race 0 elements.

Mike Barlow, a professor at University College London, and colleagues used the European Space Agency’s Herschel Space Telescope to observe the Crab Nebula 6500 light-years from the Earth in the far infrared, and found argon-hydrogen molecules.

What they observed was the argon isotope argon 36, which was ionized by the energy of a neutron star from the center of the Crab Nebula and then formed with argon-hydrogen molecules. This finding also supports the theory that the argon 36 isotope originated in the supernova center.

A hundred years after the discovery of nitrogen, the British chemist Rayleigh (JWS1842-1919), on the one hand, removed oxygen, carbon dioxide, and water vapor from the air to obtain nitrogen; on the other hand, nitrogen was decomposed from nitride.

He compared the two different sources of nitrogen and found that the density of the former is 1.2572 g / liter under normal conditions, and the density of the latter is 1.2508 g / liter. Why is the density of nitrogen in the air larger? Is there a heavier inactive gas?

The British chemist Ramsay (W.1852-1916) used the action of burning magnesium and nitrogen in the air to remove nitrogen from the air, leaving a small amount of rare gas. Spectroscopically, it proved to be a new gas element called argon.

In the following years, he used fractional distillation to separate three other Noble gases, Neon, Krypton, xenon from the crude argon. In 1895, Lemsey treated the bituminous oil ore with sulfuric acid to produce a gas that was identified by spectroscopic enthalpy.

Since he discovered helium, Neon, Krypton, argon, and xenon, he won the 1904 Nobel Prize in Chemistry.

Compounds Of Noble Gas

In the atoms of the inert gas element, the arrangement of electrons in the respective electron layers is just a stable number. Therefore, atoms are not easily lost or get electrons, and it is difficult to chemically react with other substances. Therefore, these elements are called “inert gas elements”.

In an inert gas atom with a large atomic weight and a large number of electrons, the outermost electron is far from the nucleus and is relatively weakly bound. If you encounter other atoms that attract electrons, these outermost electrons will be lost and a chemical reaction will occur.

In 1933, the famous American chemist L. Pauling predicted that hexafluoride (XeF6), hexafluoride (KrF6), citric acid and its salts could be obtained by calculating the ionic radius.

Inspired by Aintopov’s first report and Pauling’s prophecy, D.M. Younst attempted to synthesize barium fluoride and barium chloride by ultraviolet radiation and discharge, which were unsuccessful.

In the experiment of synthesizing cesium fluoride by electric discharge method, fluorine and bismuth were mixed in a certain ratio, and then a voltage of 30,000 volts was applied between the copper electrodes to perform spark discharge, but the formation of cesium fluoride was not detected.

Noble Gases

Because of the lingering fear of traditional ideas, Janster did not insist on continuing experiments, making a promising method halfway.

A series of failures have caused few people to get involved in this field in the next 30 years. Regrettably, by 1961, Pauling also denied his original prophecy, saying that “the cockroach is chemically completely unreactive, and it cannot produce the ability to usually contain covalent or ionic bond compounds”.

The development of history was dramatic, just as Pauling denied the second year of his prophecy. In 1962, the Canadian chemist N. Bartlett first synthesized bismuth and fluorine compounds.

Since 1960, several new platinum group metal fluorides have been reported in the literature, all of which are strong oxidants, and the high-valent platinum fluoride hexafluoride (PtF6) is even more oxidizing than fluorine.

Butlert first mixed with PtF6 and equimolar oxygen at room temperature to obtain a deep red solid. The chemical formula of this compound was confirmed by X-ray diffraction analysis and other experiments. The reaction equation was: O2+PtF6→ O2PtF6

Bartlett is smart, good at analogy and reasoning. He considered that the first ionization energy of O2 is 1175.7 kJ/mol, and the first ionization energy of helium is 1175.5 kJ/mol, which is slightly lower than the first ionization energy of oxygen molecules.

Since O2 can be oxidized by PtF6, then Xenon, It should also be oxidized by PtF6. He also calculated the lattice energy. If XePtF6 is formed, its lattice energy is only 41.84 kJ/mol smaller than O2PtF6. This means that once XePtF6 is generated, it should be stable.

Therefore, according to the above inference, Batllet mixed the vapor of PtF6 with equimolar hydrazine according to the method of synthesizing O2PtF6, and easily obtained an orange-yellow solid XePtF6: Xe+PtF6→XePtF6 at room temperature.

The first noble gas compound – xenon hexa fluoroplatinate (XePtF6) miraculously appeared, and with its unique experience and grace shocked the entire chemical industry, marking the establishment of noble gas chemistry, creating a rare gas chemistry A new field of research.

The compound is stable at room temperature and has a very low vapor pressure. It is insoluble in the non-polar solvent carbon tetrachloride, which means it may be an ionic compound.

It can be sublimated by heating in a vacuum, rapidly hydrolyzed when exposed to water, and evolves gas:


In June 1962, Bartlett published an important essay in the British Proceedings of the Chemical Society magazine, officially published his own experimental report to the chemical industry, which shocked the entire chemical industry.

In August of the same year, H.H. Classen directly obtained XeF4 when helium and fluorine were mixed in a volume ratio of 1:5 under heating and pressurization, and XeF2 and XeF6 were obtained at the end of the year.

The direct synthesis of ruthenium fluoride has spurred the enthusiasm of chemists to synthesize rare gas compounds.

In the short time since then, a series of different valence states of fluorinated fluorine compounds, bismuth oxyfluoride, bismuth oxyacid salts, etc. have been synthesized, and their physicochemical properties, molecular structure, and chemical bond properties have been extensively Research and discussion have greatly enriched and broadened the research field of rare gas chemistry.

By the beginning of 1963, some compounds about lanthanum and cerium were also synthesized. The smaller the atom, the stronger the electrons are bound, and the stronger the “inert” of the element, so it is more difficult to synthesize compounds of ruthenium, osmium, and argon.

Scientists at the University of Helsinki in Finland reported in the British journal Nature published on the 24th that they first synthesized a stable compound of inert gas elemental argon, hydrogen hydride, with a molecular formula of HARF.

It is a solid stable substance at low temperatures and decomposes into argon and hydrogen fluoride when heated. Scientists believe that the use of this new technology is also expected to separate the stable compounds of strontium and barium.

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In 1963, Pimentaw et al. proposed three scenarios for the preparation of HeF2 by nuclear reaction based on the similarity of the electronic arrangement of HeF2 with stable HF-2 ions:

(1) Preparation of TF-2, reuse The β decay of Tritium [3H(T)] synthesizes HeF2: TF-2→HeF2+β;

(2) radiates LiF with thermal neutrons to form HeF2;

(3) directly bombards solid fluorine with α particles to produce HeF2. However, Maugham et al. believe that although the electronic arrangement of HeF2 and HF-2 is similar, HF-2 can be regarded as an H- and two F atoms acting as a bond, and the ionization energy of H- is only 22.44 kJ. /mol and He’s ionization energy is as high as 801.5 kJ / mol, so the existence of HeF2, in theory, is questionable, whether it can form a compound, is still a mystery.

Physical and chemical properties

The air contains about 0.94% by volume of rare gases, most of which is argon.

Noble gases are colorless, odorless, tasteless, slightly soluble in water, and solubility increases with increasing molecular weight.

The molecules of Noble gases are composed of single atoms, and their melting points and boiling points are very low. As the atomic weight increases, the melting point and boiling point increase. They can be liquefied at low temperatures.

The outermost electronic structure of rare gas atoms is ns2np6, which is the most stable structure. Their properties can be explained by modern atomic structure theory: they all have a stable 8- electron configuration.

The electrons in their outermost electron layers are “full” (that is, the octagonal state has been achieved ), so they are very stable and rarely undergo chemical reactions, and only a few hundred rare gas compounds have been successfully produced to date.

The melting point and boiling point of each rare gas are very close, and the temperature difference is less than 10 °C (18 °F), so they exist in a liquid state only in a small temperature range.

The electron affinity of Noble gases is close to zero, and they have high ionization potential compared to other elements. Therefore, a rare gas atom does not easily acquire or lose electrons under normal conditions to form a chemical bond.

It shows that the chemical properties are very inactive, not only difficult to combine with other elements, but also exist in the form of monoatomic molecules. There are only weak van der Waals forces (mainly dispersive forces) between the atoms.

Helium, argon, helium, and neon are obtained from air by gas liquefaction and fractionation methods, while helium is usually extracted from natural gas, and helium is usually separated by radioactive decay of radium compounds.

Rare gases(Noble Gases) are mainly used in industry for lighting, welding and space exploration. Noble gas will also be used for diving in the deep sea. If the diving depth is greater than 55 meters, the nitrogen in the compressed air bottle used by the diver should be replaced by sputum to avoid the symptoms of oxygen poisoning and nitrogen anesthesia.

On the other hand, since the hydrogen gas is very unstable, easy combustion and explosion, today’s airships and balloons are used helium replace hydrogen.

The basic properties of the rare gas elements are listed in the table below.



Ne Ar Kr Xe


color colorless colorless colorless colorless colorless colorless
Spectral color (in the discharge tube) Pink red Blue purple Blue-green Bright white
Gas density (g/L) 0.1785 0.9002 1.7809 3.708 5.851 9.73
Melting point (K) 0.95 24.5 84.0 116.6 161.2 202.2
Boiling point (K) 4.25 27.3 87.5 120.3 166.1 208.2
Solubility (mol/L, 293K) 13.8 14.7 37.9 73 110.9
Critical temperature (K) 5.25 44.45 153.15 210.65 289.75 377.65
The heat of vaporization (kJ/mol) 0.09 1.8 6.3 9.7 13.7 18.0

*: at 2.6MPa



Ne Ar Kr Xe


Atomic number 2 10 18 36 54 86
Atomic mass 4.00 20.18 39.95 83.80 131.3 222.0
Valence electronic structure 1s 2s2p 3s3p 4s4p 5s5p 6s6p
Atomic (Van Dehua) Radius (pm) 122 160 191 198
Ith ionization potential (kJ/mol) 2372 2081 1521 1351 1170 1037
II ionization potential (kJ/mol) 5250 3952 2666 2350 2046
Constant pressure heat capacity Cp (J/K·mol) 20.79 20.79 20.79 20.79 20.79 20.79
Heat capacity quotient Cp/Cν 1.65 1.64 1.66 1.69 1.67


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

Utilizing the extremely inactive chemistry of Noble gases, some production departments often use them as protective gas. For example, in the process of soldering precision parts or active metals such as magnesium and aluminum, and manufacturing semiconductor transistors, argon is often used as a shielding gas.

Nuclear fuel reactors in nuclear reactors are also rapidly oxidized in the air and mechanically processed under argon. Filling the bulb with argon reduces the vaporization of the tungsten filament and prevents oxidation of the tungsten filament to extend the life of the bulb.

Niobium is a vehicle for gas chromatography, a filling gas for thermometers, and is used in radiation measuring equipment such as Geiger counters and bubble chambers. Both helium and argon are used as a protective gas for the welding arc and an inert shielding gas for the welding and cutting of the base metal.

They are also widely used in other metallurgical processes and in the production of silicon in the semiconductor industry.

When a rare gas is energized, it will illuminate. The world’s first neon is made of Helium (the original meaning of neon lights is “xenon “). The red light emitted by the xenon lamp has a strong transmission in the air and can pass through dense fog.

Therefore, xenon lamps are commonly used in lights on airports, ports, and water and land transportation lines. The tube is filled with argon or helium, and light blue or reddish light is emitted when energized.

Some lamps are filled with a mixture of four gases (also three or two) of helium, argon, helium, and mercury vapor. Due to the relative content of various gases, various neon lights of various colors are produced.

Fluorescent lamps commonly used in people are made by filling a small amount of mercury and argon into a tube and applying a fluorescent substance such as calcium halophosphate to the inner wall.

When energized, the tube emits ultraviolet light due to the discharge of mercury vapor, which excites the fluorescent substance to emit visible light similar to sunlight, so it is called a fluorescent lamp. Krypton can reduce the evaporation rate of the filament and is often used for incandescent lamps with higher color temperature and higher efficiency.

Especially in halogen lamps, hydrazine can be mixed with a small amount of iodine or bromine compounds. Helium is commonly used for xenon arc lamps because their near continuous spectrum is similar to daylight. This kind of lamp can be used for film projectors and car headlights.

A variety of mixed gas lasers can be fabricated using Noble gases. A helium-neon laser is one of them. The helium mixed gas is sealed in a special quartz tube.

Under the excitation of the external high-frequency oscillator, incoherent collisions occur between the atoms of the mixed gas, and energy transfer occurs between the excited atoms, thereby generating electronic transitions.

A stimulated radiation wave corresponding to the transition, near-infrared light is emitted. Helium-neon lasers can be used for measurement and communication.

Noble Gases Uses

Noble gases can be used in excimer lasers because they form excitons that are transiently present in electronically excited states (English: excimer). These excitons for the laser may be rare gas dimers such as Ar2, Kr2 or Xe2, more likely excitons bonded to halogens, such as ArF, KrF, XeF or XeCl.

These lasers produce shorter wavelengths of ultraviolet light, where ArF produces ultraviolet light at 193 nm and KrF at 248 nm. This high-frequency laser makes high precision imaging a reality.

Excimer lasers have many industrial, medical, and scientific uses. Excimer lasers must be used for microlithography and microfabrication in the fabrication of integrated circuits. Excimer lasers are also required for laser surgery, such as revascularization and eye surgery.

Helium is the lightest gas other than hydrogen. It can be placed in an airship instead of hydrogen. It will not catch fire and explode.

Noble Gas Boiling Points

The liquid helium has a boiling point of -269 ° C, which is the most difficult to liquefy in all gases. With liquid helium, an ultra-low temperature close to absolute zero (-273.15 ° C) can be obtained.

Helium is also used to replace nitrogen as artificial air for the sea divers to breathe, because in the deep sea with a large pressure, breathing with ordinary air will cause more nitrogen to dissolve in the blood.

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 bubbles, which will block the microvessels and cause “airlock”.

The solubility of helium in the blood is much smaller than that of nitrogen. This is not the case with a mixture of helium and oxygen (artificial air) instead of normal air. The liquid helium at a temperature above 2.2K is a normal liquid state and has a general liquid property.

Liquid helium with a temperature below 2.2K is a superfluid with many anomalous properties. For example, it has superconductivity, low viscosity, and the like. Its viscosity becomes one percent of the viscosity of hydrogen, and this liquid helium can flow upward along the inner wall of the container and then slowly flow down the outer wall of the container. This phenomenon makes sense for studying and validating the quantum theory.

Ionization occurs when argon is irradiated by high-energy cosmic rays. Using this principle, a counter filled with argon gas can be placed in the artificial earth satellite.

When a satellite is flying in space, argon is exposed to cosmic rays. The more intense the irradiation, the stronger the ionization of argon. The radio on the satellite automatically sends these ionization signals back to Earth, and one can determine the position and intensity of space cosmic radiation zone based on the size of the signal.

Xenon lamps also have high levels of UV radiation and can be used in medical technology. It can dissolve in the cytoplasmic oil, causing anesthesia and swelling of the cells, thus temporarily stopping the nerve endings.

A mixture of 80% bismuth and 20% oxygen has been tried as an anesthetic with no side effects. In the atomic energy industry, helium can be used to test for the presence of high-speed particles, particles, mesons, and the like.

The isotope of strontium and barium are also used to measure cerebral blood flow and the like.

Radon is the only natural radioactive gas, radon at the same time acting on the body will soon decay of radon progeny adult fitness absorbed into the body’s respiratory system caused by radiation damage induced lung cancer.

Generally, the impurities in the interior decoration materials will decay and release the helium gas, thereby causing harm to the human body. Noble gases

In vitro radiation mainly refers to the radiation effect of the radiation in the natural stone directly on the human body, which will cause damage to the hematopoietic organs, nervous system, reproductive system and digestive system in the human body.

However, niobium also has its use to seal niobium powder and tantalum in a tube. The alpha particles emitted by the decaying nucleus react with the helium nucleus, and the resulting neutrons can be used as a neutron source in the laboratory. Helium can also be used as a gas tracer to detect pipeline leaks and study gas movement.

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