As a combustible (flammable) air, hydrogen has been known for a long time. It was obtained by the action of acids on metals, the combustion and explosions of explosive gas were observed by Paracelsus, Boyle, Lemery and other scientists of the 16th - 18th centuries. With the spread of the phlogiston theory, some chemists tried to obtain hydrogen as "free phlogiston". Lomonosov's dissertation "On metallic brilliance" describes the production of hydrogen by the action of "acid alcohols" (for example, "hydrochloric alcohol", i.e. of hydrochloric acid) on iron and other metals; Russian scientist first(1745) put forward the hypothesis that hydrogen ("combustible vapor" - vapor inflammabilis) is a phlogiston. Cavendish, who studied the properties of hydrogen in detail, put forward a similar hypothesis in 1766. He called hydrogen "inflammable air" obtained from "metals" (inflammable air from metals), and believed, like all phlogistics, that when dissolved in acids, the metal loses your phlogiston. Lavoisier, who in 1779 studied the composition of water through its synthesis and decomposition, called hydrogen Hydrogine (hydrogen), or Hydrogene (hydrogen), from Greek. hydro - water and gaynome - produce, give birth.
The nomenclature commission of 1787 adopted the word production Hydrogene from gennao - I give birth. In Lavoisier's Table of Simple Bodies, hydrogen (Hydrogene) is mentioned among the five (light, heat, oxygen, nitrogen, hydrogen) "simple bodies belonging to all three kingdoms of nature and which should be considered as elements of bodies"; as old synonyms for the name Hydrogene, Lavoisier calls combustible gas (gaz inflammable), the base of combustible gas. In Russian chemical literature of the late 18th and early 19th centuries. there are two kinds of names for hydrogen: phlogistic (combustible gas, combustible air, flammable air, combustible air) and antiphlogistic (water-creating, water-creating being, water-creating gas, hydrogen gas, hydrogen). Both groups of words are translations of the French names for hydrogen.
Hydrogen isotopes were discovered in the 30s of the current century and quickly acquired great importance in science and technology. In late 1931, Urey, Breckwedd and Murphy examined the residue after prolonged evaporation of liquid hydrogen and found heavy hydrogen with an atomic weight of 2 in it. This isotope was called deuterium (Deuterium, D) from the Greek. - another, second. Four years later, in water subjected to prolonged electrolysis, an even heavier hydrogen isotope 3H was discovered, which was called tritium (Tritium, T), from the Greek. - third.
Helium, Helium, He (2)
In 1868, the French astronomer Jansen observed a total solar eclipse in India and studied the chromosphere of the sun spectroscopically. He found a bright yellow line in the spectrum of the sun, which he designated D3, which did not coincide with the yellow D line of sodium. At the same time, the same line in the spectrum of the sun was seen by the English astronomer Lockyer, who realized that it belongs to an unknown element. Lockyer, together with Frankland, for whom he then worked, decided to name the new element helium (from the Greek helios - the sun). Then a new yellow line was discovered by other researchers in the spectra of "terrestrial" products; so, in 1881, the Italian Palmieri discovered it while examining a gas sample taken from the crater of Vesuvius. The American chemist Gillebrand, while studying uranium minerals, found that they emit gases under the action of strong sulfuric acid. Hillebrand himself thought it was nitrogen. Ramsay, who drew attention to the message of Hillebrand, subjected to spectroscopic analysis the gases released during the treatment of the mineral cleveite with acid. He found that the gases contained nitrogen, argon, and an unknown gas that gave a bright yellow line. Not having a good enough spectroscope at his disposal, Ramsay sent samples of the new gas to Crookes and Lockyer, who soon identified the gas as helium. In the same year, 1895, Ramsay isolated helium from a mixture of gases; it turned out to be chemically inert, like argon. Shortly thereafter, Lockyer, Runge, and Paschen made the statement that helium consisted of a mixture of two gases, orthohelium and parahelium; one of them gives the yellow line of the spectrum, the other - green. This second gas they proposed to call Asterium (Asterium) from the Greek - stellar. Together with Travers, Ramsay checked this statement and proved that it is erroneous, since the color of the helium line depends on the pressure of the gas.
Lithium, Lithium, Li (3)
When Davy made his famous experiments on the electrolysis of alkaline earths, no one suspected the existence of lithium. Lithium alkaline earth was discovered only in 1817 by a talented analytical chemist, one of the students of Berzelius Arfvedson. In 1800, the Brazilian mineralogist de Andrada Silva, making a scientific trip to Europe, found two new minerals in Sweden, which he called petalite and spodumene, and the first of them was rediscovered a few years later on the island of Ute. Arfvedson became interested in petalite, made a complete analysis of it and found an initially inexplicable loss of about 4% of the substance. Repeating the analyzes more carefully, he found that petalite contained "a flammable alkali of a hitherto unknown nature." Berzelius suggested calling it Lithion, since this alkali, unlike potassium and sodium, was first found in the "kingdom of minerals" (stones); the name is derived from the Greek - stone. Arfwedson later discovered lithium earth, or lithine, in some other minerals, but his attempts to isolate the free metal were unsuccessful. A very small amount of lithium metal was obtained by Davy and Brande by alkali electrolysis. In 1855, Bunsen and Mattessen developed an industrial method for producing lithium metal by electrolysis of lithium chloride. In Russian chemical literature of the early 19th century. there are names: lithion, lithine (Dvigubsky, 1826) and lithium (Hess); lithium earth (alkali) was sometimes called lithin.
Beryllium, Beryllium, Be (4)
Minerals containing beryllium (precious stones) - beryl, emerald, emerald, aquamarine, etc. - have been known since ancient times. Some of them were mined on the Sinai Peninsula as early as the 17th century. BC e. The Stockholm papyrus (3rd century) describes methods for making counterfeit stones. The name beryl is found among Greek and Latin (Beryll) ancient writers and in ancient Russian works, for example, in Svyatoslav's Izbornik of 1073, where beryl appears under the name virullion. The study of the chemical composition of precious minerals of this group began, however, only at the end of the 18th century. with the onset of the chemical-analytical period. The first analyzes (Klaproth, Bindheim and others) did not find anything special in beryl. At the end of the XVIII century. the well-known mineralogist abbot Gayuy drew attention to the complete similarity of the crystal structure of beryl from Limoges and emerald from Peru. Vauquelin produced chemical analysis both minerals (1797) and found in both a new earth, different from alumina. Having received the salts of the new earth, he found that some of them have a sweet taste, which is why he named the new earth glucina (Glucina) from the Greek. - sweet. The new element contained in this earth was named accordingly glucinium. This name was used in France in the 19th century, there was even a symbol - Gl. Klaproth, being an opponent of naming new elements according to the random properties of their compounds, proposed calling glucinium beryllium (Beryllium), indicating that compounds of other elements also have a sweet taste. Beryllium metal was first obtained by Wehler and Bussy in 1728 by reducing beryllium chloride with potassium metal. We note here the outstanding research of the Russian chemist IV Avdeev on the atomic weight and composition of beryllium oxide (1842). Avdeev established the atomic weight of beryllium as 9.26 (modern 9.0122), while Berzelius took it to be 13.5, and correct formula oxide.
There are several versions about the origin of the name of the mineral beryl, from which the word beryllium is derived. A. M. Vasiliev (according to Dirgart) cites the following opinion of philologists: the Latin and Greek names of beryl can be compared with the Prakrit veluriya and the Sanskrit vaidurya. The latter is the name of a certain stone and comes from the word vidura (very far), which apparently means some country or mountain. Müller suggested another explanation: vaidurya came from the original vaidarya or vaidalya, and the latter from vidala (cat). In other words, vaidurya means approximately "cat's eye". Rai points out that in Sanskrit, topaz, sapphire, and coral were considered cat's eyes. The third explanation is given by Lippman, who believes that the word beryl meant some kind of northern country (where precious stones came from) or people. Elsewhere, Lippmann notes that Nicholas of Cusa wrote that the German Brille (glasses) comes from the barbarian-Latin berillus. Finally, Lemery, explaining the word beryl (Beryllus), indicates that Berillus, or Verillus, means "male stone."
In Russian chemical literature of the early 19th century. glucine was called sweet earth, sweet earth (Severgin, 1815), sweet earth (Zakharov, 1810), glucine, glycine, the base of glycine earth, and the element was called wisterium, glycinite, glycium, sweet earth, etc. Giese proposed the name beryllium (1814). Hess, however, stuck to the name glycia; it was also used as a synonym by Mendeleev (1st ed. of Fundamentals of Chemistry).
Borum, B (5)
Natural boron compounds (English Boron, French Bore, German Bor), mainly impure borax, have been known since the early Middle Ages. Under the names tinkal, tinkar or attinkar (Tinkal, Tinkar, Attinkar), borax was imported into Europe from Tibet; it was used for soldering metals, especially gold and silver. In Europe, tinkal was more often called borax (Borax) from the Arabic word bauraq and Persian - burah. Sometimes borax, or boraco, denoted various substances, such as soda (nitrone). Ruland (1612) calls borax chrysocolla, a resin capable of "gluing" gold and silver. Lemery (1698) also calls borax "glue of gold" (Auricolla, Chrisocolla, Gluten auri). Sometimes borax meant something like a "bridle of gold" (capistrum auri). In the Alexandrian, Hellenistic and Byzantine chemical literature, borakhi and borakhon, as well as in Arabic (bauraq) denoted alkali in general, for example, bauraq arman (Armenian borak), or soda, later they began to call borax that way.
In 1702, Gomberg, by calcining borax with iron vitriol, obtained "salt" (boric acid), which became known as "Gomberg's soothing salt" (Sal sedativum Hombergii); This salt has found wide application in medicine. In 1747, Baron synthesized borax from "soothing salt" and natron (soda). However, the composition of borax and "salt" remained unknown until the beginning of the 19th century. In the "Chemical Nomenclature" of 1787, the name horacique asid (boric acid) appears. Lavoisier in his "Table of Simple Bodies" gives a radical boracique. In 1808, Gay-Lussac and Tenard succeeded in isolating free boron from boric anhydride by heating the latter with potassium metal in a copper tube; they proposed to name the element boron (Bora) or boron (Bore). Davy, who repeated the experiments of Gay-Lussac and Tenard, also received free boron and named it boracium (Boracium). In the future, the British shortened this name to Boron. In Russian literature, the word bura is found in prescription collections of the 17th - 18th centuries. At the beginning of the XIX century. Russian chemists called boron a borer (Zakharov, 1810), buron (Strakhov, 1825), a base of buric acid, boracin (Severgin, 1815), and bohrium (Dvigubsky, 1824). The translator of Giese's book called boron a burium (1813). In addition, there are names burit, boron, buronite, etc.
Carbon, Carboneum, C (6)
Carbon (English Carbon, French Carbone, German Kohlenstoff) in the form of coal, soot and soot has been known to mankind since time immemorial; about 100 thousand years ago, when our ancestors mastered fire, they dealt with coal and soot every day. Probably, very early people got acquainted with the allotropic modifications of carbon - diamond and graphite, as well as with a fossil coal. Not surprisingly, the combustion of carbonaceous substances was one of the first chemical processes that interested the person. Since the burning substance disappeared, being consumed by fire, combustion was considered as a process of decomposition of the substance, and therefore coal (or carbon) was not considered an element. The element was fire, a phenomenon that accompanies combustion; in the teachings of the elements of antiquity, fire usually figures as one of the elements. At the turn of the XVII - XVIII centuries. the theory of phlogiston, put forward by Becher and Stahl, arose. This theory recognized the presence in each combustible body of a special elementary substance - a weightless fluid - phlogiston, which evaporates during combustion. Since only a small amount of ash remains when burning a large amount of coal, phlogistics believed that coal is almost pure phlogiston. This was the explanation, in particular, for the "phlogistic" effect of coal, its ability to restore metals from "lime" and ores. Later phlogistics - Réaumur, Bergman and others - have already begun to understand that coal is an elementary substance. However, for the first time "pure coal" was recognized as such by Lavoisier, who studied the process of burning coal and other substances in air and oxygen. In the book of Guiton de Morveau, Lavoisier, Berthollet and Fourcroix "Method of Chemical Nomenclature" (1787), the name "carbon" (carbone) appeared instead of the French "pure coal" (charbone pur). Under the same name, carbon appears in the "Table of Simple Bodies" in Lavoisier's "Elementary Textbook of Chemistry". In 1791, the English chemist Tennant was the first to obtain free carbon; he passed phosphorus vapor over calcined chalk, resulting in the formation of calcium phosphate and carbon. The fact that a diamond burns without residue when heated strongly has been known for a long time. Back in 1751 french king Franz I agreed to give a diamond and a ruby for burning experiments, after which these experiments even became fashionable. It turned out that only diamond burns, and ruby (aluminum oxide with an admixture of chromium) withstands long-term heating at the focus of the incendiary lens without damage. Lavoisier set up a new experiment on burning diamond with a large incendiary machine, and came to the conclusion that diamond is crystalline carbon. The second allotrope of carbon - graphite - in the alchemical period was considered a modified lead luster and was called plumbago; only in 1740 did Pott discover the absence of any lead impurity in graphite. Scheele studied graphite (1779) and, being a phlogisticist, considered it to be a sulfur body of a special kind, a special mineral coal containing bound "air acid" (CO2) and a large amount of phlogiston.
Twenty years later Guiton de Morveau, by gentle heating, turned the diamond into graphite and then into carbonic acid.
The international name Carboneum comes from lat. carbo (coal). The word is of very ancient origin. It is compared with cremare - to burn; root sar, cal, Russian gar, gal, goal, Sanskrit sta means boil, cook. The word "carbo" is associated with the names of carbon on other European languages(carbon, carbon, etc.). The German Kohlenstoff comes from Kohle - coal (Old German kolo, Swedish kylla - to heat). The Old Russian ugorati, or ugarati (burn, scorch) has the root gar, or mountains, with a possible transition to a goal; coal in Old Russian yug'l, or coal, of the same origin. The word diamond (Diamante) comes from the ancient Greek - indestructible, adamant, hard, and graphite from the Greek - I write.
At the beginning of the XIX century. the old word coal in Russian chemical literature was sometimes replaced by the word "coal" (Sherer, 1807; Severgin, 1815); since 1824 Solovyov introduced the name carbon. 
Nitrogen, Nitrogenium, N (7)
Nitrogen (English Nitrogen, French Azote, German Stickstoff) was discovered almost simultaneously by several researchers. Cavendish obtained nitrogen from the air (1772), passing the latter through hot coal, and then through an alkali solution to absorb carbon dioxide. Cavendish did not give a special name to the new gas, referring to it as mephitic air (Air mephitic from the Latin mephitis - suffocating or harmful evaporation of the earth). Priestley soon established that if a candle burns in the air for a long time or an animal (mouse) is located, then such air becomes unbreathable. Officially, the discovery of nitrogen is usually attributed to Black's student Rutherford, who published in 1772 a dissertation (for the degree of Doctor of Medicine) - "On fixed air, otherwise called suffocating", where some of the chemical properties of nitrogen were first described. In the same years, Scheele received nitrogen from atmospheric air in the same way as Cavendish. He called the new gas "spoiled air" (Verdorbene Luft). Since passing air through hot coal was considered by phlogistic chemists as its phlogistication, Priestley (1775) called nitrogen phlogisticated air (Air phlogisticated). Cavendish also spoke about phlogistication of air in his experience. Lavoisier in 1776 - 1777 studied in detail the composition of atmospheric air and found that 4/5 of its volume consists of asphyxiating gas (Air mofette - atmospheric mofette, or simply Mofett). The names of nitrogen - phlogisticated air, mephitic air, atmospheric mofette, spoiled air, and some others - were used before the recognition in European countries of a new chemical nomenclature, that is, before the publication of the famous book "Method of Chemical Nomenclature" (1787).
The compilers of this book - members of the nomenclature commission of the Paris Academy of Sciences - Giton de Morveau, Lavoisier, Berthollet and Fourcroix - accepted only a few new names for simple substances, in particular, the names proposed by Lavoisier for "oxygen" and "hydrogen". When choosing a new name for nitrogen, the commission, which proceeded from the principles of the oxygen theory, found itself in difficulty. As you know, Lavoisier proposed to give simple substances such names that would reflect their basic chemical properties. Accordingly, this nitrogen should be given the name "radical nitric" or "radical of nitrate acid". Such names, writes Lavoisier in his book "Principles of Elementary Chemistry" (1789), are based on the old terms nitr or saltpeter, accepted in the arts, in chemistry and in society. They would be very suitable, but nitrogen is also known to be the base of a volatile alkali (ammonia), as Berthollet had recently established. Therefore, the name radical, or the base of nitrate acid, does not reflect the main chemical properties nitrogen. Wouldn't it be better to dwell on the word nitrogen, which, according to the members of the nomenclature commission, reflects the main property of the element - its unsuitability for breathing and life. The authors of the chemical nomenclature proposed to derive the word nitrogen from the Greek negative prefix "a" and the word life. Thus, the name nitrogen, in their opinion, reflected its lifelessness, or lifelessness.
However, the word nitrogen was not coined by Lavoisier or his colleagues on the commission. It has been known since antiquity and was used by philosophers and alchemists of the Middle Ages to designate the "primary matter (base) of metals", the so-called mercury of philosophers, or the double mercury of alchemists. The word nitrogen entered the literature, probably in the first centuries of the Middle Ages, like many other encrypted and mystical names. It is found in the writings of many alchemists, starting with Bacon (XIII century) - in Paracelsus, Libavius, Valentinus and others. Libavius even indicates that the word nitrogen (azoth) comes from the ancient Spanish-Arabic word azok (azoque or azoc), denoting mercury. But it is more likely that these words appeared as a result of distortions by scribes of the root word nitrogen (azot or azoth). Now the origin of the word nitrogen is established more precisely. Ancient philosophers and alchemists considered the "primary matter of metals" to be the alpha and omega of everything that exists. In turn, this expression is borrowed from the Apocalypse - last book Bible: "I am the alpha and omega, the beginning and the end, the first and the last." In ancient times and in the Middle Ages, Christian philosophers considered it proper to use only three languages recognized as "sacred" when writing their treatises - Latin, Greek and Hebrew (the inscription on the cross at the crucifixion of Christ according to the Gospel story was made in these three languages). To form the word nitrogen, the initial and final letters of the alphabets of these three languages (a, alpha, aleph and zet, omega, tov - AAAZOT) were taken.
The compilers of the new chemical nomenclature of 1787, and above all the initiator of its creation, Giton de Morvo, were well aware of the existence of the word nitrogen since ancient times. Morvo noted in the "Methodical Encyclopedia" (1786) the alchemical meaning of this term. After the publication of the Method of Chemical Nomenclature, opponents of the oxygen theory - phlogistics - came out with sharp criticism of the new nomenclature. Especially, as Lavoisier himself notes in his textbook of chemistry, the adoption of "ancient names" was criticized. In particular, La Mettrie, publisher of the journal Observations sur la Physique, a stronghold of opponents of the oxygen theory, pointed out that the word nitrogen was used by the alchemists in a different sense.
Despite this, the new name was adopted in France, as well as in Russia, replacing the previously accepted names "phlogisticated gas", "mofette", "mofette base", etc.
The word formation nitrogen from the Greek also caused fair remarks. DN Pryanishnikov in his book "Nitrogen in the life of plants and agriculture in the USSR" (1945) correctly noted that word formation from the Greek "raises doubts." Obviously, Lavoisier's contemporaries also had these doubts. Lavoisier himself in his textbook of chemistry (1789) uses the word nitrogen along with the name "radical nitrique" (radical nitrique).
It is interesting to note that later authors, apparently trying to somehow justify the inaccuracy made by the members of the nomenclature commission, derived the word nitrogen from the Greek - life-giving, life-giving, creating an artificial word "azotikos", which is absent in the Greek language (Dirgart, Remy and etc.). However, this way of forming the word nitrogen can hardly be recognized as correct, since the derivative word for the name nitrogen should have sounded "azoticon".
The failure of the name nitrogen was obvious to many of Lavoisier's contemporaries, who were in full sympathy with his oxygen theory. So, Chaptal in his chemistry textbook "Elements of Chemistry" (1790) proposed replacing the word nitrogen with the word nitrogen (nitrogen) and called the gas, according to the views of his time (each molecule of gas was represented by an atmosphere of caloric), "nitrogen gas" (Gas nitrogene). Chaptal motivated his proposal in detail. One of the arguments was the indication that the name, meaning lifeless, could with great reason be given to other simple bodies (possessing, for example, strong poisonous properties). The name nitrogen, adopted in England and America, later became the basis for the international name of the element (Nitrogenium) and the symbol for nitrogen - N. In France at the beginning of the 19th century. instead of the symbol N, the symbol Az was used. In 1800, one of the co-authors of the chemical nomenclature, Fourcroix, proposed another name - alkaligen (alcaligen - alcaligene), based on the fact that nitrogen is the "base" of volatile alkali (Alcali volatil) - ammonia. But this name was not accepted by chemists. Finally, let us mention the name of nitrogen, which was used by phlogistic chemists and, in particular, by Priestley, at the end of the 18th century. - septon (Septon from the French Septique - putrid). This name was proposed, apparently, by Mitchell, a student of Black, who later worked in America. Davy rejected this title. in Germany since the end of the eighteenth century. and to this day nitrogen is called Stickstoff, which means "suffocating substance".
As for the old Russian names for nitrogen, which appeared in various works of the late 18th - early 19th centuries, they are as follows: suffocating gas, unclean gas; mofetic air (all these are translations of the French name Gas mofette), suffocating substance (translation of the German Stickstoff), phlogisticated air, gas burnt, burnt air (phlogistic names are a translation of the term proposed by Priestley - Рlogisticated air). Names were also used; spoiled air (translation of Scheele's term Verdorbene Luft), saltpeter, saltpeter gas, nitrogen (translation of the name proposed by Chaptal - Nitrogene), alkaligen, alkaline agent (Furcroix's terms translated into Russian in 1799 and 1812), septon, putrefactive (Septon ) and others. Along with these numerous names, the words nitrogen and nitrogen gases were also used, especially from the beginning of the 19th century.
V. Severgin in his "Guide to the most convenient understanding of foreign chemical books" (1815) explains the word nitrogen as follows: "Azoticum, Azotum, Azotozum - nitrogen, suffocating substance"; "Azote - Nitrogen, saltpeter"; "nitrate gas, nitrogen gas". Finally, the word nitrogen entered the Russian chemical nomenclature and replaced all other names after the publication of "Fundamentals of Pure Chemistry" by G. Hess (1831).
Derivative names of compounds containing nitrogen are formed in Russian and other languages either from the word nitrogen ( Nitric acid, azo compounds, etc.), or from the international name nitrogenium (nitrates, nitro compounds, etc.). The latter term comes from the ancient names nitr, nitrum, nitrone, which usually denoted saltpeter, sometimes natural soda. Ruland's dictionary (1612) says: "Nitrum, pine forest (baurach), saltpeter (Sal petrosum), nitrum, among the Germans - Salpeter, Vergsalz - the same as Sal retrae."
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Oxygen, Oxygenium, O(8)
The discovery of oxygen (English Oxygen, French Oxygene, German Sauerstoff) marked the beginning of the modern period in the development of chemistry. Since ancient times, it has been known that air is needed for combustion, but for many centuries the combustion process remained incomprehensible. Only in the XVII century. Mayow and Boyle, independently of each other, expressed the idea that the air contains some substance that supports combustion, but this completely rational hypothesis was not developed at that time, since the concept of combustion as a process of connecting a burning body with a certain constituent part of the air seemed to while contradicting such an obvious fact as the fact that during combustion the decomposition of a burning body into elementary components takes place. It is on this basis at the turn of the XVII century. the theory of phlogiston, created by Becher and Stahl, arose. With the onset of the chemical-analytical period in the development of chemistry (second half of the 18th century) and the emergence of "pneumatic chemistry" - one of the main branches of the chemical-analytical direction - combustion, as well as respiration, again attracted the attention of researchers. The discovery of various gases and the establishment of them important role in chemical processes was one of the main stimuli for the systematic studies of the processes of combustion of substances undertaken by Lavoisier. Oxygen was discovered in the early 70s of the 18th century. The first report of this discovery was made by Priestley at a meeting of the English Royal Society in 1775. Priestley, heating red mercury oxide with a large burning glass, obtained a gas in which the candle burned more brightly than in ordinary air, and the smoldering torch flashed. Priestley determined some of the properties of the new gas and called it daphlogisticated air. However, two years earlier, Priestley (1772) Scheele also obtained oxygen by decomposition of mercury oxide and other methods. Scheele called this gas fiery air (Feuerluft). Scheele was able to make a report about his discovery only in 1777. Meanwhile, in 1775, Lavoisier spoke to the Paris Academy of Sciences with the message that he managed to get "the purest part of the air that surrounds us," and described the properties of this part of the air. At first, Lavoisier called this "air" empirical, vital (Air empireal, Air vital), the basis of vital air (Base de l "air vital). The almost simultaneous discovery of oxygen by several scientists in different countries caused disputes over priority. Priestley was especially persistent in recognizing himself as a discoverer. In essence, these disputes have not ended so far. A detailed study of the properties of oxygen and its role in the processes of combustion and the formation of oxides led Lavoisier to the wrong conclusion that this gas is an acid-forming principle. In 1779, Lavoisier, in accordance with this conclusion, introduced a new name for oxygen - the acid-forming principle (principe acidifiant ou principe oxygine). The word oxygine appearing in this complex name was derived by Lavoisier from the Greek. - acid and "I produce".
Fluorine, Fluorum, F (9)
Fluorine (English Fluorine, French and German Fluor) was obtained in a free state in 1886, but its compounds have been known for a long time and were widely used in metallurgy and glass production. The first mention of fluorite (CaF2) under the name of fluorspar (Fliisspat) dates back to the 16th century. One of the works attributed to the legendary Vasily Valentin mentions stones painted in various colors - fluxes (Fliisse from Latin fluere - flow, pour), which were used as fluxes in the smelting of metals. Agricola and Libavius write about the same. The latter introduces special names for this flux - fluorspar (Flusspat) and mineral melt. Many authors of chemical and technical writings of the 17th and 18th centuries. describe different types fluorspar. In Russia, these stones were called plavik, spalt, spat; Lomonosov classified these stones as selenites and called them spar or flux (crystal flux). Russian masters, as well as collectors of mineral collections (for example, in the 18th century, Prince P.F. Golitsyn) knew that some types of spars glow in the dark when heated (for example, in hot water). However, even Leibniz in his history of phosphorus (1710) mentions in this connection thermophosphorus (Thermophosphorus).
Apparently, chemists and artisan chemists became acquainted with hydrofluoric acid no later than the 17th century. In 1670, the Nuremberg craftsman Schwanhard used fluorspar mixed with sulfuric acid to etch designs on glass goblets. However, at that time the nature of fluorspar and hydrofluoric acid was completely unknown. It was believed, for example, that silicic acid has an etching effect in the Schwanhard process. This erroneous opinion was eliminated by Scheele, proving that in the interaction of fluorspar with sulfuric acid, silicic acid is obtained as a result of the erosion of the glass retort by the resulting hydrofluoric acid. In addition, Scheele established (1771) that fluorspar is a compound of calcareous earth with a special acid, which was called "Swedish acid". Lavoisier recognized the hydrofluoric acid radical (radical fluorique) as a simple body and included it in his table of simple bodies. More or less pure hydrofluoric acid was obtained in 1809 by Gay-Lussac and Tenard by distillation of fluorspar with sulfuric acid in a lead or silver retort. During this operation, both researchers were poisoned. The true nature of hydrofluoric acid was established in 1810 by Ampère. He rejected Lavoisier's opinion that hydrofluoric acid must contain oxygen, and proved the analogy of this acid with hydrochloric acid. Ampère reported his findings to Davy, who shortly before that had established the elemental nature of chlorine. Davy fully agreed with Ampere's arguments and spent a lot of effort on obtaining free fluorine by electrolysis of hydrofluoric acid and in other ways. Taking into account the strong corrosive effect of hydrofluoric acid on glass, as well as on plant and animal tissues, Ampere suggested calling the element contained in it fluorine (Greek - destruction, death, pestilence, plague, etc.). However, Davy did not accept this name and proposed another - fluorine (Fluorine) by analogy with the then name of chlorine - chlorine (Chlorine), both names are still used in English language. In Russian, the name given by Ampere has been preserved.
Numerous attempts to isolate free fluorine in the 19th century did not lead to successful results. Only in 1886 did Moissan manage to do this and obtain free fluorine in the form of a yellow-green gas. Since fluorine is an unusually aggressive gas, Moissan had to overcome many difficulties before he found a material suitable for the apparatus in experiments with fluorine. The U-tube for electrolysis of hydrofluoric acid at minus 55°C (cooled with liquid methyl chloride) was made of platinum with fluorspar plugs. After the chemical and physical properties free fluorine, it has found wide application. Now fluorine is one of the most important components of fluorine synthesis. organic matter a wide range. Russian literature of the early 19th century. fluorine was called differently: the base of hydrofluoric acid, fluorine (Dvigubsky, 1824), fluorine (Iovsky), fluor (Shcheglov, 1830), fluor, fluorine, fluorine. Hess from 1831 introduced the name fluorine.
Neon, Neon, Ne (10)
This element was discovered by Ramsay and Travers in 1898, a few days after the discovery of krypton. Scientists have selected the first bubbles of the gas formed during the evaporation of liquid argon, and found that the spectrum of this gas indicates the presence of a new element. Ramsay talks about choosing a name for this element like this:
“When we first looked at his spectrum, my 12-year-old son was there.
“Father,” he said, “what is the name of this beautiful gas?”
"It's not decided yet," I replied.
- He's new? - inquired the son.
“Newly discovered,” I objected.
“Why not call him Novum then, father?”
"That doesn't fit because novum is not a Greek word," I replied. We'll call it neon, which means new in Greek.
This is how the gas got its name.
Author: Figurovsky N.A.
Chemistry and Chemists № 1 2012
To be continued...
The superdense state of the Universe did not last long, but it played a decisive role in the subsequent development. At enormous values of temperature and density of matter, intense processes of interconversion of particles and radiation quanta began. At first, particles and their corresponding antiparticles from photons were born in equal quantities. high energy. Under the conditions of the superdense state of matter, which is characteristic of the early stage of the life of the Universe, particles and antiparticles would have to collide again immediately after their birth, turning into gamma radiation. This mutual transformation of particles into radiation and back continued until the photon energy density exceeded the threshold energy of particle formation.
In the early stages of the development of the Universe, extremely short-lived and very massive hypothetical particles could arise. As the temperature and density dropped (age reached 0.01 sec, temperature 10 11 K), less massive particles began to appear, while more massive ones “died out” due to annihilation or decay.
The extinction of particles did not occur in exactly the same way, so that the antiparticles practically all disappeared, and an insignificant excess fraction of protons and neutrons remained. As a result, the observable world turned out to be made of matter, and not of antimatter, although somewhere in the Universe there may be regions of antimatter.
Without a barely noticeable asymmetry in the properties of particles and antiparticles, the world would generally be devoid of matter.
The formation of nucleons (protons and neutrons) ends the era of hadrons in the evolution of the Universe (hadrons are particles subject to strong interactions: protons, neutrons, mesons, etc.). After the hadron era, the lepton era begins, when the medium consists mainly of positive and negative muons, neutrinos and antineutrinos, positrons and electrons. Nucleons are rare. As the Universe expands further, muons, electrons, and positrons annihilate. Then the interaction of the neutrino with matter stops, and by the time of 0.2 seconds after the singularity, the neutrino is detached.
Approximately 10 seconds after the singularity, the temperature reaches a value of about 10 10 K and the era of radiation begins. At this stage, photons still strongly interacting with matter, as well as neutrinos, predominate in number.
A huge number of electrons and positrons turned into radiation in a catastrophic process of mutual annihilation, leaving behind a small number of electrons, however, enough to unite with protons and neutrons to give rise to the amount of matter that we observe today in the Universe.
3 minutes after the Big Bang, the first processes of nucleosynthesis begin. Some of the protons manage to combine with neutrons and form helium nuclei. They moved about 10% total number protons. The era of radiation ends with the transition of the plasma from the ionized state to the neutral state, a decrease in the opacity of matter, and the “separation” of radiation. A minute later, almost all the matter of the Universe consisted of nuclei of hydrogen and helium, which were in the same proportion that we observe today. Starting from this moment, the expansion of the primary fireball proceeded without significant changes until, after 700,000 years, electrons and protons did not combine into neutral hydrogen atoms, then the Universe became transparent to electromagnetic radiation - relict background radiation arose.
A million years after the beginning of the expansion, the era of matter begins, when the diversity of the present world began to develop from hot hydrogen-helium plasma with a small admixture of other nuclei.
After the matter became transparent to electromagnetic radiation, gravitation came into action, it began to prevail over all other interactions between the masses of practically neutral matter, which constituted the main part of the matter of the Universe. Gravity has created galaxies, clusters, stars and planets.
There are many unanswered questions in this picture. Did galaxies form before the first generation of stars, or vice versa? Why was the substance concentrated in discrete formations - stars, galaxies, clusters, while the Universe as a whole flew apart in different directions?
The inhomogeneities in the Universe, from which all the structural formations of the Universe subsequently formed, originated in the form of insignificant fluctuations, and then intensified in the era when the ionized gas in the Universe began to turn into a neutral one, i.e. when the radiation broke away from the substance and became relic. Such amplification can lead to the appearance of noticeable fluctuations, from which galaxies subsequently began to form.
In the formation of large structures of the Universe, neutrinos could play a significant role if their rest mass is different from zero. A few hundred years after the beginning of the expansion, the speed of neutrinos with mass should become noticeably less than the speed of light. Starting from a certain moment, large concentrations of neutrinos no longer dissolve and give rise to large structural formations of the Universe - clusters and superclusters of galaxies. The galaxies themselves are formed from ordinary matter, and neutrinos, if they have a noticeable mass, act as centers of gravity for giant mass concentrations, being the source of the hidden mass of galaxy clusters.
In 1978, M. Rees suggested that background radiation could be the result of an “epidemic” of the formation of massive stars that began immediately after the separation of radiation from matter and before the age of the Universe reached 1 billion years. The lifetime of such stars could not exceed 1 billion years. Many of them exploded like supernovae and threw heavy chemical elements into space, which partially gathered into grains. solid matter, forming clouds of interstellar dust. This dust, heated by the radiation of pre-galactic stars, could emit infrared radiation, which is now observed as the microwave background radiation. If this hypothesis is correct, then this means that the vast majority of the entire mass of the Universe is contained in the invisible remnants of the stars of the first, pre-galactic, generation and may currently be located in massive dark halos surrounding bright galaxies.
Education process chemical elements in the Universe is inextricably linked with the evolution of the Universe. We have already become acquainted with the processes taking place near big bang”, we know some details of the processes that took place in the “primary soup” of elementary particles. The first atoms of chemical elements, which are at the beginning of the table of D. I. Mendeleev (hydrogen, deuterium, helium), began to form in the Universe even before the appearance of the first generation of stars. It was in the stars, their depths, warmed up again (after the Big Bang, the temperature of the Universe began to drop rapidly) to billions of degrees, and the nuclei of chemical elements following helium were produced. Considering the importance of stars as sources, generators of chemical elements, let us consider some stages of stellar evolution. Without understanding the mechanisms of star formation and the evolution of stars, it is impossible to imagine the process of formation of heavy elements, without which, ultimately, life would not have arisen. Without stars in the Universe, a hydrogen-helium plasma would have existed forever, in which the organization of life is obviously impossible (at the current level of understanding of this phenomenon).
We have previously noted three observational facts or tests of modern cosmology, extending over hundreds of parsecs, now we point out the fourth - the abundance of light chemical elements in space. It should be emphasized that the formation of light elements in the first three minutes and their abundance in the modern Universe was first calculated in 1946 by an international trinity of outstanding scientists: the American Alpher, the German Hans Bethe and the Russian Georgy Gamow. Since then, atomic and nuclear physicists have repeatedly calculated the formation of light elements in the early universe and their abundance today. It can be argued that the standard model of nucleosynthesis is well supported by observations.
The evolution of the stars. The mechanism of formation and evolution of the main objects of the Universe - stars, has been studied most xoponio. Here, scientists were helped by the opportunity to observe a huge number of stars at various stages of development - from birth to death - including many so-called "stellar associations" - groups of stars born almost simultaneously. The comparative "simplicity" of the structure of the star, which is quite successfully amenable to theoretical description and computer simulation, also helped.
Stars are formed from gas clouds, which, under certain circumstances, break up into separate "clumps", which are further compressed under the influence of their own gravity. The compression of the gas under the influence of its own gravity is prevented by the rising pressure. With adiabatic compression, the temperature must also increase - gravitational binding energy is released in the form of heat. As long as the cloud is rarefied, all the heat easily escapes with radiation, but in the dense core of the condensation, the removal of heat is difficult, and it quickly heats up. The corresponding increase in pressure slows down the compression of the core, and it continues to occur only due to the gas that continues to fall on the born star. As the mass increases, the pressure and temperature in the center increase, until finally the latter reaches a value of 10 million Kelvin. At that moment, nuclear reactions begin in the center of the star, converting hydrogen into helium, which maintain the stationary state of the newly formed star for millions, billions or tens of billions of years, depending on the mass of the star.
The star turns into a huge thermonuclear reactor, in which, in general, the same reaction that a person has learned to carry out only in an uncontrolled version - in hydrogen bomb. The heat released during the reaction stabilizes the star, maintaining internal pressure and preventing its further contraction. A small random increase in the reaction slightly "inflates" the star, and the corresponding decrease in density leads again to a weakening of the reaction and stabilization of the process. The star "burns" with almost constant brightness.
The temperature and radiation power of a star depends on its mass, and depends non-linearly. Roughly speaking, with an increase in the mass of a star by 10 times, the power of its radiation increases by 100 times. Therefore, more massive, hotter stars use up their fuel reserves much faster than less massive ones, and live relatively short lives. The lower limit of the mass of a star, at which it is still possible to achieve temperatures sufficient to start at the center thermonuclear reactions, is approximately 0.06 solar. The upper limit is about 70 solar masses. Accordingly, the faintest stars shine several hundred times weaker than the Sun and can shine like that for a hundred billion years, much longer than the time of the existence of our Universe. Massive hot stars can shine a million times stronger than the Sun and live only a few million years. The time of the stable existence of the Sun is approximately 10 billion years, and of this period it has lived for half so far.
The stability of a star is broken when a significant part of the hydrogen in its interior burns out. A helium core devoid of hydrogen is formed, and the combustion of hydrogen continues in a thin layer on its surface. At the same time, the core contracts, in the center of its pressure and temperature rises, at the same time, the upper layers of the star, located above the layer of hydrogen combustion, on the contrary, expand. The diameter of the star grows, and the average density decreases. Due to the increase in the area of the radiating surface, its total luminosity also slowly increases, although the surface temperature of the star decreases. The star turns into a red giant. At some point in time, the temperature and pressure inside the helium core are sufficient to start the next reactions of synthesis of heavier elements - carbon and oxygen from helium, and at the next stage even heavier ones. In the depths of a star, many elements can be formed from hydrogen and helium. Periodic system, but only up to the elements of the iron group, which has the highest binding energy per particle. Heavier elements are formed in other rarer processes, namely, in the explosions of supernovae and partially new stars, and therefore they are few in nature.
We note an interesting, paradoxical, at first glance, circumstance. As long as hydrogen is burning near the center of the star, the temperature there cannot rise to the threshold of the helium reaction. To do this, it is necessary that the burning stops, and the core of the star begins to cool! The cooling core of the star contracts, while the strength of the gravitational field increases and gravitational energy is released, which heats the substance. With increased field strength, a higher temperature is needed so that the pressure can withstand compression, and gravitational energy is sufficient to provide this temperature. We have a similar paradox when a spacecraft descends: in order to transfer it to a lower orbit, it must be slowed down, but at the same time it turns out to be closer to the Earth, where gravity is stronger, and its speed will increase. Cooling down increases temperature, and braking increases speed! Nature is full of such seeming paradoxes, and it is far from always possible to trust "common sense".
After the start of helium combustion, energy consumption proceeds very rapidly, since the energy yield of all reactions with heavy elements is much lower than in the hydrogen combustion reaction, and, in addition, the total luminosity of the star at these stages increases significantly. If hydrogen burns for billions of years, then helium for millions, and all other elements for no more than thousands of years. When all nuclear reactions in the interior of a star die out, nothing can prevent its gravitational contraction, and it happens catastrophically fast (collapses, as they say). The upper layers fall towards the center with free fall acceleration (its value exceeds the earth's acceleration of fall by many orders of magnitude due to the incommensurable mass difference), releasing huge gravitational energy. The substance is compressed. Part of it, moving into a new state high density, forms a remnant star, and a part (usually large) is ejected into space in the form of a reflected shock wave at great speed. A supernova explosion occurs. (In addition to gravitational energy, the kinetic energy of the shock wave also contributes to the thermonuclear afterburning of a part of the hydrogen remaining in the outer layers of the star, when the falling gas is compressed near the stellar core - an explosion of a grandiose "hydrogen bomb" occurs).
At what stage in the evolution of a star the compression will stop and what will be the remnant of a supernova, all these options depend on its mass. If this mass is less than 1.4 solar masses, it will be a white dwarf, a star with a density of 10 9 kg/m 3 , slowly cooling without internal energy sources. It is kept from further compression by the pressure of the degenerate electron gas. With a larger mass (up to about 2.5 solar), a neutron star is formed (their existence was predicted by the great Soviet physicist, Nobel laureate Lev Landau) with a density approximately equal to the density atomic nucleus. neutron stars were discovered as the so-called pulsars. With an even greater initial mass of the star, a black hole is formed - an uncontrollably contracting object that no object, even light, can leave. It is during supernova explosions that the formation of elements heavier than iron occurs, for which extremely dense streams of high-energy particles are needed in order for multi-particle collisions to be sufficiently probable. Everything material in this world is the descendants of supernovae, including people, since the atoms of which we are composed, arose sometime during supernovae explosions.
Thus, stars are not only a powerful source of energy High Quality, the scattering of which contributes to the emergence of the most complex structures, including life, but also by reactors in which the entire periodic table is produced - the necessary material for these structures. The explosion of a star ending its life throws into space a huge amount of various elements heavier than hydrogen and helium, which mix with galactic gas. During the life of the Universe, many stars have ended their lives. All stars such as the Sun and more massive, which have arisen from the primary gas, have already passed their life path. So now the Sun and similar stars are stars of the second generation (and maybe third), significantly enriched in heavy elements. Without such enrichment, terrestrial-type planets and life could hardly have arisen near them.
Here is information about the prevalence of some chemical elements in the Universe:
As you can see from this table, hydrogen and helium are the predominant chemical elements at present (almost 75% and 25% each). The relatively low content of heavy elements, however, turned out to be sufficient for the formation of life (at least on one of the islands of the Universe near an "ordinary" star, the Sun - a yellow dwarf). In addition to what we have already mentioned earlier, we must remember that in open space there are cosmic rays, which in fact are streams of elementary particles, primarily electrons and protons of different energies. In some areas of interstellar space there are local areas of increased concentration of interstellar matter, called interstellar clouds. In contrast to the plasma composition of a star, the matter of interstellar clouds already contains (this is evidenced by numerous astronomical observations) molecules and molecular ions. For example, interstellar clouds of molecular hydrogen H 2 have been discovered, and compounds such as the OH hydroxyl ion, CO molecules, water molecules, etc. are very often present in the absorption spectra. Now the number of those detected in interstellar clouds chemical compounds is over one hundred. Under the influence of external radiation and without it, various chemical reactions, often such that it is impossible to implement on Earth due to special conditions in the interstellar medium. Probably, about 5 billion years ago, when our solar system was formed, the primary material in the formation of planets were the same simple molecules that we now observe in other interstellar clouds. In other words, the process of chemical evolution, which began in the interstellar cloud, then continued on the planets. Although quite complex organic molecules have now been found in some interstellar clouds, it is likely that chemical evolution has led to the appearance of "living" matter (that is, cells with mechanisms of self-organization and heredity) only on planets. It is very difficult to imagine the organization of life in the volume of interstellar clouds.
Planetary chemical evolution.
Consider the process of chemical evolution on Earth. The primary atmosphere of the Earth contained mainly the simplest hydrogen compounds H 2 , H 2 O, NH 3 , CH 4 . In addition, the atmosphere was rich in inert gases, primarily helium and neon. At present, the abundance of noble gases on Earth is negligible, which means that they once dissonated into interplanetary space. Our modern atmosphere is of secondary origin. At first, the chemical composition of the atmosphere differed little from the primary one. After the formation of the hydrosphere, ammonia NH 3 practically disappeared from the atmosphere, dissolved in water, atomic and molecular hydrogen escaped into interplanetary space, the atmosphere was saturated mainly with nitrogen N. The saturation of the atmosphere with oxygen occurred gradually, first due to the dissociation of water molecules by the ultraviolet radiation of the Sun, then, and the main through plant photosynthesis.
It is possible that a certain amount of organic matter was brought to Earth during the fall of meteorites and, possibly, even comets. For example, comets contain compounds such as N, NH 3 , CH 4 and others. It is known that the age of the earth's crust is approximately 4.5 billion years. There are also geological and geochemical data indicating that already 3.5 billion years ago earth atmosphere was rich in oxygen. Thus, the primary atmosphere of the Earth existed for no more than 1 billion years, and life arose, probably even earlier.
At present, significant experimental material has been accumulated, illustrating how such simple substances as water, methane, ammonia, carbon monoxide, ammonium and phosphate compounds are converted into highly organized structures that are the building blocks of the cell. American scientists Kelvin, Miller and Urey conducted a series of experiments, as a result of which it was shown how amino acids could arise in the primary atmosphere. Scientists have created a mixture of gases - methane CH 4 , molecular hydrogen H 2 , ammonia NH 3 and water vapor H 2 O, simulating the composition of the Earth's primary atmosphere. Electric discharges were passed through this mixture, as a result, glycine, alanine and other amino acids were found in the initial mixture of gases. Probably, the Sun exerted a significant influence on chemical reactions in the Earth's primary atmosphere with its ultraviolet radiation, which was not retained in the atmosphere due to the absence of ozone.
Not only electrical discharges and ultraviolet radiation from the Sun, but also volcanic heat, shock waves, radioactive decay of potassium K (the share of the decay energy of potassium about 3 billion years ago on Earth was second, after the energy of the ultraviolet radiation of the Sun) had an important role in chemical evolution. For example, gases released from primary volcanoes (O 2, CO, N 2, H 2 O, H 2, S, H 2 S, CH 4, SO 2), when exposed to various kinds energies react with the formation of various small organic compounds, such as: hydrogen cyanide HCN, formic acid HCO 2 H, acetic acid H 3 CO 2 H, glycine H 2 NCH 2 CO 2 H, etc. Later, again, when exposed to various types of energy, small organic compounds react with the formation of more complex organic compounds: amino acids
Thus, on Earth there were conditions for the formation of complex organic compounds necessary for the creation of a cell.
At present, there is still no single logically consistent picture of how life arose from the primary “superdrop of matter” called the Universe after the Big Bang. But already many elements of this picture scientists imagine and believe that this is how everything really happened. One of the elements of this unified picture of evolution is chemical evolution. Perhaps, chemical evolution is one of the argued elements of a unified picture of evolution, if only because it allows experimental modeling of chemical processes (which, for example, cannot be done with respect to conditions similar to those near the “big bang”). Chemical evolution can be traced down to the elementary building blocks of living matter: amino acids, nucleic acids.
14.1 Stages of element synthesis
In order to explain the prevalence in nature of various chemical elements and their isotopes, in 1948 Gamow proposed a model of the Hot Universe. According to this model, all chemical elements were formed at the time of the Big Bang. However, this claim was subsequently refuted. It has been proven that only light elements could be formed at the time of the Big Bang, while heavier ones arose in the processes of nucleosynthesis. These positions are formulated in the Big Bang model (see item 15).
According to the Big Bang model, the formation of chemical elements began with the initial nuclear fusion of light elements (H, D, 3 He, 4 He, 7 Li) 100 seconds after the Big Bang at a Universe temperature of 10 9 K.
The experimental basis of the model is the expansion of the Universe observed on the basis of redshift, the initial synthesis of elements and cosmic background radiation.
The big advantage of the Big Bang model is the prediction of the abundance of D, He and Li, which differ from each other by many orders of magnitude.
Experimental data on the abundance of elements in our Galaxy showed that hydrogen atoms are 92%, helium - 8%, and heavier nuclei - 1 atom per 1000, which is consistent with the predictions of the Big Bang model.
14.2 Nuclear fusion - synthesis of light elements (H, D, 3 He, 4 He, 7 Li) in the early Universe.
- The abundance of 4 He or its relative fraction in the mass of the Universe is Y = 0.23 ±0.02. At least half of the helium produced in the Big Bang is contained in intergalactic space.
- The original deuterium exists only inside the Stars and quickly turns into 3 He.
Observational data yield the following limits on the abundance of deuterium and He with respect to hydrogen:
10 -5 ≤ D/H ≤ 2 10 -4 and
1.2 10 -5 ≤ 3 He/H ≤ 1.5 10 -4 ,
moreover, the observed ratio D/H is only a fraction of ƒ from the initial value: D/H = ƒ(D/H) initial. Since deuterium quickly turns into 3 He, the following estimate for abundance is obtained:
[(D + 3 He)/H] initial ≤ 10 -4 .
- It is difficult to measure the abundance of 7 Li, but data on the study of stellar atmospheres and the dependence of the abundance of 7 Li on the effective temperature are used. It turns out that, starting from a temperature of 5.5·10 3 K, the amount of 7 Li remains constant. The best estimate of the average abundance 7 Li is:
7 Li/H = (1.6±0.1) 10 -10 .
- The abundance of heavier elements such as 9 Be, 10 V and 11 V is several orders of magnitude less. Thus, the prevalence is 9 Be/N< 2.5·10 -12 .
14.3 Synthesis of nuclei in Main Sequence stars at T< 108 K
Synthesis of helium in stars Main Sequence in pp- and CN-cycles occurs at a temperature of T ~ 10 7 ÷7·10 7 K. Hydrogen is processed into helium. Nuclei of light elements arise: 2 H, 3 He, 7 Li, 7 Be, 8 Be, but there are few of them due to the fact that they subsequently enter into nuclear reactions, and the 8 Be nucleus almost instantly decays due to the short lifetime (~ 10 -16 s)
8 Be → 4 He + 4 He.
The process of synthesis seemed to have to stop, But nature has found a workaround.
When T > 7 10 7 K, helium "burns out", turning into carbon nuclei. There is a triple helium reaction - "Helium flash" - 3α → 12 C, but its cross section is very small and the process of formation of 12 C goes in two stages.
The fusion reaction of 8Be and 4He nuclei occurs with the formation of a 12C* carbon nucleus in an excited state, which is possible due to the presence of a level of 7.68 MeV in the carbon nucleus, i.e. reaction takes place:
8 Be + 4 He → 12 C* → 12 C + γ.
The existence of the energy level of the 12 C nucleus (7.68 MeV) helps to bypass the short lifetime of 8 Be. Due to the presence of this level, the nucleus 12 C occurs Breit-Wigner resonance. The 12 C nucleus passes to an excited level with energy ΔW = ΔM + ε,
where εM = (M 8Be − M 4He) − M 12C = 7.4 MeV, and ε is compensated by the kinetic energy.
This reaction was predicted by the astrophysicist Hoyle and then reproduced in the laboratory. Then the reactions begin:
12 C + 4 He → 16 0 + γ
16 0 + 4 He → 20 Ne + γ and so on up to A ~ 20.
So the required level of the 12 C nucleus made it possible to overcome the bottleneck in the thermonuclear fusion of elements.
The nucleus 16 O does not have such energy levels and the reaction of formation of 16 O is very slow
12 C + 4 He → 16 0 + γ.
These features of the course of reactions led to the most important consequences: thanks to them, the same number of 12 C and 16 0 nuclei turned out to be, which created favorable conditions for the formation organic molecules, i.e. life.
A change in the level of 12 C by 5% would lead to a catastrophe - further synthesis of elements would stop. But since this did not happen, then nuclei are formed with A in the range
| A = 25÷32 |
This leads to the values A
All Fe, Co, Cr nuclei are formed by thermonuclear fusion.
It is possible to calculate the abundance of nuclei in the Universe based on the existence of these processes.
Information about the abundance of elements in nature is obtained from the spectral analysis of the Sun and Stars, as well as cosmic rays. On fig. 99 shows the intensity of the nuclei at different values of A.
Rice. 99: The abundance of elements in the universe.
Hydrogen H is the most abundant element in the universe. Lithium Li, beryllium Be, and boron B are 4 orders of magnitude smaller than neighboring nuclei and 8 orders of magnitude smaller than H and He.
Li, Be, B are good fuels, they quickly burn out already at T ~ 10 7 K.
It is more difficult to explain why they still exist - most likely due to the process of fragmentation of heavier nuclei at the protostar stage.
IN cosmic rays Li, Be, B nuclei are much larger, which is also a consequence of the processes of fragmentation of heavier nuclei during their interaction with the interstellar medium.
12 C ÷ 16 O is the result of the Helium flash and the existence of a resonant level in 12 C and the absence of one in 16 O, the core of which is also doubly magic. 12 C - semi-magical core.
Thus, the maximum abundance of iron nuclei is 56 Fe, and then a sharp decline.
For A > 60, the synthesis is energetically unfavorable.
14.5 Formation of nuclei heavier than iron
The fraction of nuclei with A > 90 is small - 10 -10 of hydrogen nuclei. The processes of formation of nuclei are associated with side reactions occurring in stars. There are two such processes:
s (slow) − slow process,
r (rapid) is a fast process.
Both of these processes are associated with neutron capture those. it is necessary that conditions arise under which many neutrons are produced. Neutrons are produced in all combustion reactions.
13 C + 4 He → 16 0 + n - helium combustion,
12 C + 12 C → 23 Mg + n - carbon flash,
16 O + 16 O → 31 S + n − oxygen flash,
21 Ne + 4 He → 24 Mg + n − reaction with α-particles.
As a result, the neutron background accumulates and s- and r-processes can occur - neutron capture. When neutrons are captured, neutron-rich nuclei are formed, and then β-decay occurs. It turns them into heavier nuclei.
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The emergence of chemical elements
1. The emergence of the universe
Most cosmologists believe that the Universe originated as a dense bunch of matter and energy, which began to expand about 18 billion years ago. The formation of elements has its roots in the Big Bang. The emergence of elements as a result of the Big Bang was first substantiated by Gamow in 1946 (Gamov, 1946).
According to Gamow, in the early stages of the formation of the Universe, temperatures and pressures were extremely high, while protons, neutrons, electrons and neutrinos were in equilibrium. When the universe began to expand, the temperature dropped and the state of equilibrium was disturbed. Gamow believed that the successive repetition of the processes of decay and capture of neutrons led to the formation of heavy elements. It only took about 20 minutes. for the origin of all currently existing elements, but it is currently believed that light elements were formed during the Big Bang, which then, through nuclear reactions inside stars, gave rise to elements with atomic number 6 and higher (Ozima, 1990).
Initially, most of the matter existed in the form of energy. The substance began to take shape as it cooled. The general picture of the occurrence of elements can be expressed by the following scheme.
"Combustion" of hydrogen. In the process of nuclear fusion, hydrogen atoms fuse together to form a helium atom and release energy. The mass of particles that make up helium is: 2 protons (1.0076 each) and 2 neutrons (1.0089 each) = 2 1.0076 + 2 1.0089 = 4.033. The nucleus of a helium atom has a mass of 4.0028. A decrease of 0.0302 units of mass is called the mass defect, which, according to the Einstein equation E = mc2, is equivalent to 4.512 J atom-1. This process requires a temperature of 107 - 108 K:
"Combustion" of helium occurs at a temperature > 108 K and a pressure of 105 g cm2.
2. Star formation
Hydrogen and other light elements scattered into the universe and, grouped together, formed stars. Under the influence of their own gravity, the stars began to gradually shrink, which led to an increase in temperature. When the temperature at the center of each of the stars reached several million degrees, the hydrogen atoms combined and formed helium atoms, i.e. the reaction of "burning" of the nuclei. Then came the atoms of C and other heavy elements.
Thus, the elementary composition of the Universe is determined by nuclear processes in stars. Thus, a temperature of 108 K is possible inside a star with a mass equal to that of our sun. The process of nuclear transformations is constantly going on inside the sun:
Rice. 1. Schematic representation of our sun
It can be seen that these reactions can be represented as an autocatalytic cycle known as the Bethe-von Weizsäcker carbon cycle (Fig. 2).
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Rice. 2. Bethe carbon cycle - von Weizsäcker
In stars with large masses, the temperatures are higher and there processes of synthesis of heavier elements take place. In stars twice as heavy as the sun (Fig. 3):
Rice. 3. Stars twice (a), three times (b) heavier than the Sun and a star before a supernova explosion (c).
Stars with a mass of 20 solar masses (Fig. 3) are capable of synthesizing all elements, up to iron. But the nuclear "burning" reactions cannot develop beyond the formation of Fe nuclei. After that, such a reaction leads to the energy instability of the nuclei. The Fe nuclei can be considered as the completion of thermonuclear reactions (r-processes). Iron (No. 26) has the most stable core. Each step of nuclear fusion from helium to iron releases energy and forms a more stable core (Figure 4). With the passage of time, the amount of hydrogen and helium in the Universe decreases, while the amount of heavy elements increases. The relative abundance of elements in the Universe is shown in fig. 5.
Rice. 4. Stability of nuclei of chemical elements
The nuclei of all elements after iron are less stable than the original material and cannot be used to form stellar energy. Elements #27 (Mg) to #92 (U) are formed when a star depletes its nuclear fuel, collapses and explodes as a supernova. The shock wave from a supernova explosion produces the excess energy needed to fuse elements heavier than iron.
Rice. 5. Relative abundance of elements in the Universe.
Neutrons are produced in stars during the "burning" of He. Since they are devoid of charge, they are relatively easy to incorporate into nuclei. Absorbing neutrons and undergoing reactions - the decay of the nucleus gradually "get heavier". This reaction is called the s-process. It is believed that Bi is the end product of the s-process. Some of the elements formed are unstable and spontaneously decay to more stable substances. This process, nuclear decay, comes with the release of energy.
3. History of the environmental chemistry scene
Emergence solar system
It is now generally accepted that the elements that now make up the solar system and our earth, for the most part, arose as a result of nuclear reactions in stars. The exceptions are H (it is believed that it has existed since the formation of the Universe), He and several light elements (D, Li, Be, B), which were formed from H during the Big Bang (Ozima, 1990).
Since the decay rate of most heavy elements is well known, it is possible to calculate the exact age of substances containing long-lived isotopes. So was the age of our solar system determined? 5 billion years. Since the mass of the Sun is insufficient for the formation of heavy elements, it should be assumed that the solar system was formed at the site of a supernova explosion. Gravitational forces gathered the scattered matter. Most of it was concentrated in the form of the Sun, hot enough to start the process of nuclear fusion.
The planets of the solar system were formed, apparently, from a disk-shaped cloud of hot gases, the remnants of a supernova explosion. The condensed vapors formed solid particles that combined into small bodies (planetesimals), as a result of which the dense inner planets arose (from Mercury to Mars). The large outer planets, being more distant from the Sun, are composed of gases of lower density, the condensation of which occurred at much lower temperatures.
Almost all the atoms of our system are concentrated in the Sun, where more than 99.9% of the mass of the entire matter of the system is concentrated. From the point of view of the chemical composition of the solar system as a whole, the Earth consists mainly of oxygen and non-volatile elements (such as Fe, Mg, Si), with the proportion of the latter<< 0,1 % от общего числа атомов Солнечной системы (Озима, 1990).
Most elements were formed before the formation of the solar system, during the explosion of a supernova, but some appeared after, during the decay of radioactive isotopes. For example, it was found that almost all (more than 99%) argon, which makes up about 1% of the Earth's atmosphere, arose as a result of the 40K 40Ar decay reaction in the Earth's interior after its formation and subsequently volatilized. All other elements, except for radiogenic elements. Radiogenic elements - elements that arose as a result of nuclear decay reactions. - Already existed before the emergence of the solar system.
The emergence and history of the Earth
Earth formation
The formation of the Earth was associated with the accumulation of solar gas matter. Concerning a way of accumulation of the uniform opinion does not exist. There are currently three main hypotheses (Voitkevich, 1988).
Homogeneous accumulation. The modern shell structure of the Earth arose only in the course of heating, partial melting and differentiation of the initially homogeneous terrestrial matter.
heterogeneous accumulation. First, a metallic core arose, then late condensates in the form of silicates settled on it, forming a thick mantle.
Partially heterogeneous accumulation. The greatest difference in composition existed only between the central parts of the planet and its surface layers. Initially, there were no sharp boundaries between the core and the mantle, which were established later.
Most of the planetary matter was grouped 4.56-4.7 billion years ago. The mass of the planet continued to grow and after some time became sufficient to hold the atmosphere (4.4 billion years ago).
The oldest rocks on Earth are the zircons of Western Australia, which are about 4.1-4.3 billion years old. The heat released first by the process of accretion and then by radioactive decay melted the core of the planet and gave rise to the geothermal cycle. This caused the differentiation of elements, first explained by V. M. Goldshidt.
The primary differentiation of the elements was carried out according to their chemical affinity for iron, which is natural, since iron makes up 35% of the Earth's mass.
V.M. Goldschmidt divided the elements into 4 groups:
Siderophiles - are restored by iron;
Lithophiles - are not reduced by iron and are prone to the formation of oxides;
Chalcophiles - elements that are not reduced by iron and form sulfides;
Atmophiles are elements that have escaped into the atmosphere.
Elements occupying minima on the atomic volume curve form alloys with iron; in the course of differentiation, they formed the earth's core (siderophile elements). Siderophile ions (11 elements) have a shell of 8-18 electrons. Their redox potential is equal to or higher than that of iron. Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Mo, W, Re, Au, Ge, Sn make up the majority of polymetallic ores. They are closely interspersed with the elements, showing an increased affinity for sulfur, arsenic, as well as phosphorus, carbon and nitrogen.
The elements occupying the maxima on the curve and located on its descending parts have an affinity for oxygen (54 elements), they formed the earth's crust and upper mantle (lithophile elements). They form ions with an 8-electron shell. Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, B, Al, Sc, Y, Rare earth elements, Si, Ti, Zr, Hf, Th, P, V, Nb, Ta, Cr , U, F. Cl, Br, I, Mn This group also includes “facultative” lithophile elements: C, P, W, H, Tl, Ga, Ge, Fe. are part of silicate, aluminosilicate rocks, form sulfate, carbonate, phosphate, borate and halide minerals.
The elements occupying the ascending parts of the curve have an affinity for sulfur, selenium, tellurium (19 elements), they are concentrated in the lower mantle (chalcophile elements). They have a shell of 18 electrons. Cu, Ag, Zn, Cd, Hg, Ga, In, Tl, Bp, As, Sb, Bi, S, Se, Te Fe, Mo, Ca are "facultative" chalcophiles. form a large group of sulfide and telluride minerals. They may occur in a native state.
Inert gases (He, Ne, Ar, Kr, Xe, Rn) belong to the atmophilic group. Their atoms (except for He) have an 8-electron shell.
Currently, biophiles are also isolated. Biophilic elements are the so-called elements of life. They are divided into macrobiogenic (H, C, N, O, Cl, Br, S, P, Na, K, Mg, Ca) and microbiogenic (V, Mn, Fe, Co, Cu, Zn, B, Si, Mo, F).
The modern biogeochemical classification of elements is shown in Table 1.
Table 1 Biogeochemical classification of elements
gamov universe biogeochemical thermonuclear
Mantle differentiation and formation of geospheres
During the formation of the planet, low-melting, but heavy components (iron-sulphurous masses) were smelted, descending to the center and forming the core. At the same time, sidero- and chalcophile elements were carried to the core from the primary mantle. At the same time, less fusible silicate masses formed basaltic magma, and then oceanic-type basaltic crust. Litho- and atmophilic elements were mainly involved in this process.
During the melting and degassing of the upper mantle, basaltic magma was brought to the Earth's surface, carrying water and gases dissolved in it. Both the primary atmosphere and the primary hydrosphere of the Earth arose due to degassing of the mantle. From the vapors of the mantle material, an acidic, highly mineralized hydrosphere arose, initially rich in F-, Cl-, Br-, I- anions. Fresh water was formed as a result of natural distillation. At the same time, a reducing primary atmosphere was formed.
Atmospheric evolution
The atmosphere is made up of gases that surround the Earth, and its composition has changed significantly since the formation of the planet. For a long time the point of view dominated that the primary atmosphere of the Earth consisted mainly of ammonia and methane.
Earth's first atmosphere was lost to space in the first million years after accretion. This atmosphere consisted of gases trapped inside the planetoids that formed the Earth. It consisted of carbon dioxide and nitrogen with trace amounts of methane, ammonia, sulfur dioxide and hydrochloric acid. There was no oxygen.
The second atmosphere of the Earth supposedly contained carbon dioxide, nitrogen, water. With the cooling of the surface of the planet, oceans formed, the hydrological cycle and weathering processes began. In addition, the oceans began to intensively absorb carbon dioxide. The conditions that existed on the surface of the planet at that time are mostly unknown, since the intensity of solar radiation was 30% lower than today, and the exact composition of the atmosphere is unclear.
Bacterial photosynthesis began between 3.5-4 billion years ago, but almost all of the oxygen was taken up by the ocean (mostly iron ions). Two billion years ago, oxygen began to enter the atmosphere, and the current composition of the atmosphere was formed about 1.5 billion years ago. In the atmosphere, oxygen under the action of ultraviolet radiation formed ozone. Ozone acted as a filter for the harsh solar radiation, allowing life to emerge onto land from the ocean.
The emergence of life
The emergence of the biosphere belongs to the earliest periods of the development of the planet. The first known fossilized remains of living organisms (age - 3.55 billion years) were discovered in Western Australia by William Schopf. They are extremely similar in structure to modern cyanobacteria (otherwise called blue-green algae), rather highly developed photosynthetics. Geochemical data indicate that photoautotrophic life existed on the planet 4 billion years ago. From a biological point of view, heterotrophic life should have preceded it. But, how and, most importantly, when did it have time to arise?
The centuries-old struggle to prove the impossibility of the emergence of living things from non-living things ended with the triumphant experiments of L. Pasteur, which, it would seem, put an end to this dispute. But then it turned out that life could only be created by God. The materialistic science of the twentieth century could not come to terms with this. AI Oparin in 1924, and then J. Haldane in 1929 put forward the hypotheses of biogenesis - the possibility of spontaneous generation of life on Earth (see Oparin, 1960; Bernal, 1969). Generally speaking, many hypotheses of the origin of life were created, the experimental basis of which was, mainly, the possibility of synthesizing the simplest organic compounds under the conditions of the ancient Earth, as we now imagine them. The impetus for this was the discovery by Miller of the ease of formation of amino acids from inorganic precursors (Miller, 1953). As L. Margelis writes (1983, p. 76): “The purists slandered that this is supposedly worthless experimental organic chemistry, which consists in creating an environment supposedly similar to the Hadean eon, which began when the Earth turned into a continuous solid body, inorganic reagents are introduced into it and energy is supplied, and then among the reaction products they look for molecules that are important for modern life. This approach gave rise to many works that proved the possibility of synthesizing rather complex organic substances under the conditions of the ancient Earth (see, for example, the works of Horowitz (Horowitz, 1962), Ponnamperuma (1968), Fox (1975), essay by N. L. Dobretsov (2005) and many others). At the same time, “the data of the cosmochemistry of meteorites, asteroids, and comets indicate that the formation of organic compounds in the solar system at the early stages of its development was a typical and massive phenomenon” (Voitkevich, 1988, p. 105).
Any person who knows biology at least within the elementary course imagines that for the emergence of life were necessary:
evolution of small molecules;
the formation of polymers from them;
the emergence of their catalytic functions;
self-assembly of molecules;
the emergence of membranes and the creation of precellular organization;
the emergence of the mechanism of heredity;
cell formation.
If we turn to S. Lem, better known as a science fiction writer than a scientist, then he writes: “The implementation of each specific stage on the way to the appearance of the pracell had a certain probability. The emergence of amino acids in the primary ocean under the influence of electrical discharges was, for example, quite probable, the formation of peptides from them was a little less, but also quite feasible; on the other hand, the spontaneous synthesis of enzymes is, from this point of view, a super-unusual phenomenon” (Lem, 2002, p. 48). And, further: “Thermodynamics can still “swallow” the random occurrence of proteins in a solution of amino acids, but the spontaneous generation of enzymes no longer passes ... The number of possible enzymes is greater than the number of stars in the entire Universe. If the proteins in the primordial ocean had to wait for the spontaneous production of enzymes, this could successfully last for an eternity” (Lem, 2002, p. 49). The origin of life, as a result, is proved only by “the simple fact that we exist and, therefore, we ourselves are an indirect argument in favor of biogenesis” (Lem, 2002, p. 50).
Far from being a science fiction writer comes to the same conclusion, but the Nobel Prize winner, one of the founders of modern molecular biology, co-author of the discovery of DNA - the “molecule of life”, F. Crick, who, having specifically dwelled on the negligible probability of spontaneous generation of life, further writes: “He himself the fact that we are here necessarily means that life really began” (Crick, 2002, p. 77).
IN AND. Vernadsky generally believes that “all questions about the beginning of life on Earth, if there was one, should be left without consideration ... These questions entered science from outside, originated outside of it - in the religious or philosophical quest of mankind ... All of us known, precisely established facts in nothing will not change, even if all these problems receive a negative solution, i.e., if we admit that life has always been and had no beginning, that the living - the living organism - has never and nowhere originated from inert matter, and that in the history of the Earth there were generally geological epochs devoid of life” (Vernadsky, 2004, p. 53).
Critical Atmospheric Oxygen Levels
According to L. Berkner and L. Marshall (1966, cited by Perelman, 1973), in the abiogenic epoch, the oxygen content did not exceed 0.1% of the current level. Oxygen was formed due to the photodissociation of water. Life under such conditions could develop only in reservoirs with a depth of more than 12 m. Upon reaching the level of oxygen content of 1% of the modern one, the possibility of absorbing ultraviolet radiation was created. The area of life has expanded significantly, since 30 cm of water has become enough to retain ultraviolet radiation. This level was reached at the beginning of the Paleozoic era (about 600 million years ago). In just 20 million years, many new species arose, and the accumulation of oxygen in the atmosphere accelerated. Already after 200 million years (the end of the Silurian, 400-420 million years ago), the oxygen content reached 10% of the modern one. The ozone shield became so powerful that life could come to land. This led to a new explosion of evolution.
Stages of evolution of the biosphere
The kingdom of mammals and angiosperms began 60 million years ago, i.e., the biosphere acquired a look close to modern. 6 million years ago, a group of primates emerged, which are the direct and immediate ancestors of modern man - hominids. 600,000 years ago Homo sapiens appeared, about 60,000 years ago he mastered fire and thus stood out sharply from nature. The emergence of modern civilization can be attributed to a period of about 6 thousand years ago, and the emergence of the modern mode of production and the beginning of the New Age.
6 centuries ago. The anthropogenic impact on the environment reached global scale, perhaps, by the middle of the 20th century.
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