Gold is a chemical element: complete characteristics. Gold is a chemical element: full characteristics Origin and name of gold from the periodic table

Gold(lat. Aurum), Au, chemical element 1 group of Mendeleev's periodic system; atomic number 79, atomic mass 196.9665; heavy yellow metal. Consists of one stable isotope 197 Au.

Historical reference. Z. was the first metal known to man. Products from earth were found in cultural layers of the Neolithic era (5th-4th millennium BC). In ancient states - Egypt, Mesopotamia, India, China, the extraction of gold, the manufacture of jewelry and other items from it existed 3-2 thousand BC. e. Z. is often mentioned in the Bible, the Iliad, the Odyssey and other monuments of ancient literature. Alchemists called Z. “the king of metals” and designated it with the symbol of the Sun; the discovery of ways to transform base metals into gold was the main goal alchemy.

For the development of Z. mining, see Noble metals.

Prevalence in nature. The average gold content in the lithosphere is 4.3·10 -7% by mass. Gold is dispersed in magma and igneous rocks, but from hot waters in the earth's crust hydrothermal gold deposits are formed, which are of great industrial importance (quartz gold-bearing veins, etc.). In ores, gold is mainly found in a free (native) state (see. Native gold) and only very rarely forms minerals with selenium, tellurium, antimony, and bismuth. Pyrite and other sulfides often contain an admixture of gold, which is extracted during the processing of copper, polymetallic, and other ores.

In the biosphere, gold migrates in combination with organic compounds and mechanically in river suspensions. 1 liter of sea and river water contains about 4·10 -9 G Z. In areas of gold ore deposits, groundwater contains Z. approximately 10 -6 g/l. It migrates in soils and from there enters plants; some of them concentrate nutrients, such as horsetails and corn. The destruction of endogenous gold deposits leads to the formation of gold placers, which are of industrial importance. Gold is mined in 41 countries; its main reserves are concentrated in the USSR, South Africa and Canada.

Physical and Chemical properties. Z. is a soft, very ductile, malleable metal (can be forged into sheets up to 8·10 -5 thick mm, stretched into wire, 2 km which weigh 1 G), conducts heat and electricity well, and is very resistant to chemical influences. Crystal cell Z. face-centered cubic, a = 4.704 Å. Atomic radius 1.44 Å, ionic radius Au 1+ 1.37 Å. Density (at 20°C) 19.32 g/cm 3, t pl 1064.43°C, t kip 2947°C; thermal coefficient of linear expansion 14.2·10 -6 (0-100°C); thermal conductivity 311.48 Tue/(m·TO) ; specific heat capacity 132.3 j/(kg·K) (at 0 -100°C); electrical resistivity 2.25·10 -8 ohm(m(2.25·10 -6 ohm(cm) (at 20°C); temperature coefficient of electrical resistance 0.00396 (0-100°C). Modulus of elasticity 79 103 Mn/m 2(79 10 2 kgf/mm 2), for annealed steel, the tensile strength is 100-140 Mn/m 2(10-14 kgf/mm 2), relative elongation 30-50%, narrowing of the cross-sectional area 90%. After plastic deformation in the cold, the tensile strength increases to 270-340 Mn/m 2 (27-34 kgf/mm 2). Brinell hardness 180 Mn/m 2 (18 kgf/mm 2) (for annealed gold about 400 °C).

Configuration of the outer electrons of the Z atom. 5d 10 6s 1 . In compounds, gold has valencies of 1 and 3 (complex compounds are known in which gold is 2-valent). Z. does not interact with nonmetals (except halogens). Z forms halides with halogens, for example 2Au + 3Cl 2 = 2AuC13. Z. dissolves in a mixture of hydrochloric and nitric acids, forming chlorauric acid H. In solutions of sodium cyanide NaCN (or potassium KCN), with simultaneous access to oxygen, chloride is converted into sodium cyanoaurate (I) 2Na. This reaction, discovered in 1843 by P.R. Bagration, received practical application only at the end of the 19th century. (cm. Cyanidation). Z. is characterized by its easy reduction from compounds to metal and the ability to form complexes. The existence of oxide oxide, i.e. oxide oxide (I) Au 2 O, is doubtful. Chloride Z. (I) AuCl is obtained by heating chloride Z. (III): AuC1 3 = AuCl + C1 2.

Z. chloride (III) AuC1 3 is obtained by the action of chlorine on powder or thin leaves of gold at 200 °C. Red needles AuC1 3 give a brown-red solution of complex acid with water: AuC1 3 +H 2 O=H 2.

When a solution of AuC1 3 is deposited with caustic alkali, amphoteric yellow-brown hydroxide III (III) Au (OH) 3 with predominant acidic properties precipitates; therefore it is called golden acid, and its salts are called aurates (III). When heated, hydroxide (III) transforms into oxide Au 2 O 3, which above 220 decomposes according to the reaction:

2Au 2 O 3 = 4Au + 3O 2.

When reducing salts of Z. with tin (II) chloride 2AuC1 3 + 3SnCl 2 = 3SnCl 4 + 2Au

a very stable purple colloidal solution of Z. (Cassian purple) is formed; this is used in analysis to detect gold. Quantitative determination of gold is based on its precipitation from aqueous solutions with reducing agents (FeSO 4, H 2 SO 3, H 2 C 2 O 4, etc.) or on the use assay analysis.

Obtaining gold and its refining. Gold can be extracted from placer deposits by elutriation, based on the large difference in the densities of gold and waste rock. This method, which was already used in ancient times, is associated with large losses. He gave way amalgamation(known already in the 1st century BC and used in America since the 16th century) and cyanidation, which became widespread in America, Africa and Australia in the 1890s. At the end of the 19th - beginning of the 20th centuries. The main source of gold was primary deposits. The gold-bearing rock is first crushed and enriched. Z is extracted from the resulting concentrate with a solution of potassium or sodium cyanide. Zinc is precipitated from a solution of complex cyanide with zinc; At the same time, impurities also fall out. To purify (refine) gold by electrolysis (the method of E. Wollwill, 1896), anodes cast from unclean gold are suspended in a bath containing a hydrochloric acid solution of AuC1 3, and a sheet of pure gold serves as the cathode. When a current passes, impurities precipitate (anodic sludge , sludge), and gold is deposited on the cathode with a purity of at least 99.99%.

Application. Z. in the conditions of commodity production performs the function money(see section Economic significance). In technology, gold is used in the form of alloys with other metals, which increases the strength and hardness of gold and makes it possible to save it (see. Gold alloys The gold content in alloys used for the manufacture of jewelry, coins, medals, semi-finished products for dental prosthetic production, etc. is expressed as breakdown (see. Try noble metals, Jewelry alloys); Usually the additive is copper (the so-called alloy). When alloyed with platinum, gold is used in the production of chemically resistant equipment; when alloyed with platinum and silver, it is used in electrical engineering. Z. compounds are used in photography (tinting).

S. A. Pogodin.

Z . in art. Z. has been used since ancient times in jewelry art(decorations, cult and palace utensils, etc.), as well as for gilding. Thanks to its softness, malleability, and ability to stretch, gold lends itself to particularly fine processing by embossing, casting, and engraving. Z. is used to create a variety of decorative effects (from the smooth surface of a yellow polished surface with smooth tints of light highlights to complex textured juxtapositions with a rich play of light and shadow), as well as to perform the finest filigree. Z., often colored with impurities of other metals in various colors, used in combination with precious and ornamental stones, pearls, enamel, mob.

In medicine, Z. preparations are used in the form of a suspension in oil (the domestic drug Krizanil, the foreign one - myocrisin) or water-soluble drugs (foreign ones - Sancrizin and Solganal) for injection in the treatment of chronic rheumatoid arthritis, erythematous lupus erythematosus, often in combination with hormonal drugs, etc. drugs. Z. drugs often cause side effects(increased body temperature, irritation of the intestines, kidneys, etc.). Contraindications to the use of Z. drugs: severe forms of tuberculosis, diabetes mellitus, diseases of the cardiovascular system, liver, kidneys, blood.

Radioactive gold (usually 198 Au) is injected into tissues in the form of pins, granules, etc. - For gamma therapy and in the form of colloidal solutions - for beta therapy. It is used in the treatment of tumors, usually in combination with surgery and drug treatment, as well as for diagnostic purposes - in the form of colloidal solutions in the study of the reticuloendothelial system, liver, spleen and other organs.

Lit.: Plaksin I.N., Gold, in the book: Brief Chemical Encyclopedia, vol. 2, M., 1966; Remi G., Course of inorganic chemistry, trans. from German, vol. 2, M., 1966, p. 439-451; Ullmanns Enzykiopädie dertechnischen Chemie, 3 Aufl., Bd 8, Münch. - B., 1957, S. 253-307; Magakyan I.G., Ore deposits, 2nd ed., Yerevan, 1961; Russian gold and silver crafting of the 15th-20th centuries, M., 1967 (bib. p. 289-93); Rosenberg M., Geschichte der Goldschmiedekunst auf technischer Grundlage, Fr./M., 1918.

Economic significance. In conditions of commodity production, gold performs the function of a universal equivalent. “The first function of gold is to provide the commodity world with material for expressing value, that is, in order to express the values ​​of goods as quantities of the same name, qualitatively identical and quantitatively comparable” (Marx K., in the book: Marx K. and Engels F., Soch., 2nd ed., vol. 23, p. 104). Expressing the value of all other goods, money as a general equivalent acquires a special use value and becomes money. “Gold and silver are not money by nature, but money by nature is gold and silver” (K. Marx, ibid., vol. 13, p. 137). The commodity world singled out gold as money because it has the best physical and chemical properties for a monetary commodity: homogeneity, divisibility, storability, portability (high value for small volume and weight), and easy to process. A significant amount of gold is used to make coins or is stored in the form of bars as the gold reserve of central banks (states). Gold is widely used for industrial consumption (in radio electronics, instrument making, and other progressive industries), and also as a material for the manufacture of jewelry.

Initially gold was used exclusively for making jewelry, then it began to serve as a means of saving and accumulating wealth, as well as exchange (first in the form of ingots). Gold was used as money as early as 1500 BC. e. in China, India, Egypt and the states of Mesopotamia, and in Ancient Greece - in the 8th-7th centuries. BC e. In Lydia, rich in mineral deposits, in the 7th century. BC e. The minting of the first coins in history began. The name of the Lydian king Croesus (reigned around 560-546 BC) became synonymous with untold wealth. On the territory of the USSR (in Armenia), coins from Z. were minted in the 1st century. BC e. But in ancient times and in the Middle Ages, gold was not the main currency metal. Along with it, the functions of money were performed by copper and silver.

The pursuit of wealth and the passion for enrichment were the causes of numerous colonial and trade wars; during the era of the Great Geographical Discoveries, they pushed people to search for new lands. Flow precious metals to Europe after the discovery of America was one of the sources initial capital accumulation. Until the middle of the 16th century. From the New World to Europe, mainly gold was imported (97-100% of the imported metal), and from the 2nd third of the 16th century, after the discovery of the richest silver deposits in Mexico and Peru, mainly silver (85-99%). In Russia at the beginning of the 19th century. New mineral deposits began to be developed in the Urals and Siberia, and for three decades the country ranked first in the world in its production. In the middle of the 19th century. Rich gold deposits were discovered in the USA (California) and Australia in the 1880s. - in the Transvaal (South Africa). The development of capitalism and the expansion of intercontinental trade increased the demand for monetary metals, and although gold production increased, in all countries, along with gold, silver continued to be widely used as money. At the end of the 19th century. There was a sharp decrease in the cost of silver due to the improvement of methods for its extraction from polymetallic ores. The growth of world gold production and especially its influx into Europe and the United States from Australia and Africa accelerated the displacement of depreciated silver and created the conditions for the transition of most countries to monometallism (gold) in its classical form of the gold coin standard (see. gold standard). The first to switch to gold monometallism was at the end of the 18th century. Great Britain. To the head of the 20th century. gold currency has established itself in most countries of the world.

Reflecting the relationships of people in the conditions of spontaneous commodity production, the power of wealth appears on the surface of phenomena as a relationship between things, seems to be a natural internal property of wealth and gives rise to gold and money fetishism (see. Money, Commodity fetishism). The passion for accumulating gold wealth grows limitlessly and pushes people to commit monstrous crimes. Z.'s power especially increases under capitalism when labor becomes a commodity. The formation of a world market under capitalism expanded the sphere of circulation of money and made it world money.

During the period of the general crisis of capitalism, the gold standard is undermined. In the internal circulation of capitalist countries, paper money and irredeemable banknotes become dominant. The export of gold and its purchase and sale are limited or completely prohibited. In this regard, money ceases to perform the functions of a means of circulation and a means of payment, but, ideally acting as a measure of value, and also retaining the significance of a means of creating treasures and world money, it remains the basis of monetary systems and the main means of final settlement of mutual monetary claims and obligations of capitalist countries . The size of gold reserves is an important indicator of the stability of capitalist currencies and the economic potential of individual countries (see also gold reserve, Gold reserves). The purchase and sale of gold for industrial consumption, as well as for private hoarding (accumulation), is carried out in special gold markets (see. Gold markets). The loss of currency from free interstate market circulation caused a reduction in its share in the monetary system of the capitalist world and, above all, in the foreign exchange reserves of capitalist countries (from 89% in 1913 to 71% in 1928, 69% in 1958 and 55% in 1969). An increasingly significant portion of the newly mined gold is supplied for hoarding and industrial use (in the modern chemical industry, rocket science, and space technology). Thus, during 1960-70, private gold hoarding increased by 3.3 times, its industrial and jewelry use by almost 2.3 times, and the gold reserves of capitalist countries remained at almost the same level ($41 billion). (For the extraction of gold in capitalist countries, see Art. Gold mining industry.)

In a socialist economy, money is also a universal equivalent, serving as a measure of value and a scale of prices. On January 1, 1961, the gold content of the Soviet ruble was set at 0.987412 G net Z. This same amount of Z. is used as the basis for the transferable ruble - the international socialist currency of the CMEA member countries. In the world socialist market, money performs the function of world money.

Lit.: Mikhalevsky F.I., Gold during the World Wars, [M.], 1945; his, Gold in the system of capitalism after the Second World War, M., 1952; Borisov S. M., Gold in the economics of modern capitalism, M., 1968.

A. I. Stadnichenko.

Gold- element of group 11 (according to the outdated classification - a secondary subgroup of the first group), the sixth period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 79. Denoted by the symbol Au (lat. Aurum). The simple substance gold is a noble metal of yellow color. Registration number CAS: 7440-57-5.

Pure gold is a soft yellow metal. The reddish hue of some gold products, such as coins, is given by impurities of other metals, in particular copper. In thin films, gold shows through green. Gold has high thermal conductivity and low electrical resistance.
Gold is a very heavy metal: the density of pure gold is 19.321 g/cm³ (a ball of pure gold with a diameter of 46.237 mm has a mass of 1 kg). Among metals it ranks sixth in density: after osmium, iridium, rhenium, platinum and plutonium. The high density of gold makes it easier to mine. The simplest technological processes, such as, for example, flushing at sluices, can provide a very high degree of gold recovery from the washed rock.

Element 79 of the periodic table Gold is a very soft metal: hardness on the Mohs scale is ~2.5, on the Brinell scale 220-250 MPa (comparable to the hardness of a nail).

Gold is also highly ductile: it can be forged into sheets up to ~0.1 µm thick (gold leaf); With such a thickness, gold is translucent and in reflected light has a yellow color, in transmitted light it is colored bluish-greenish, complementary to yellow. Gold can be drawn into wire with a linear density of up to 2 mg/m.
The melting point of gold is 1064.18 °C (1337.33 K), boils at 2856 °C (3129 K). The density of liquid gold is less than solid gold and is 17 g/cm3 at the melting point. Liquid gold is quite volatile and actively evaporates long before its boiling point.
Linear coefficient of thermal expansion - 14.2·10-6 K−1 (at 25 °C). Thermal conductivity - 320 W/m K, specific heat capacity - 129 J/(kg K), electrical resistivity - 0.023 Ohm mm2/m.

Electronegativity according to Pauling is 2.4. The electron affinity energy is 2.8 eV; atomic radius 0.144 nm, ionic radii: Au+ 0.151 nm (coordination number 6), Au3+ 0.082 nm (4), 0.099 nm (6).

Ruthenium, rhodium, palladium, osmium, iridium and sometimes rhenium. The above metals received this name due to their high chemical resistance. Gold has been highly valued all over the world since ancient times. Its special value is evidenced by the fact that any medieval alchemist considered the goal of his life to obtain gold from other substances, most often used as the starting material. There are legends that some, such as Nicolas Flamel, even succeeded.

Gold and its history

Incredibly, gold is the very first metal that humanity recognized! Its discovery dates back to the Neolithic era, i.e. approximately 11,000 years ago! Gold was widely used in all ancient civilizations, it was called the “king of metals” and was designated by the same hieroglyph as the sun. There are archaeological finds of gold jewelry that was made in the third millennium BC. e.
The entire history of mankind is closely connected with gold. The vast majority of wars before the use of oil were fought precisely because of this noble metal. As Goethe aptly noted in his Faust: “People die for metal!” Gold was one of the prerequisites for the Great Geographical Discoveries, i.e. period in history during which Europeans discovered new continents and sea routes to Africa, America, Asia and Oceania. In the 15th century, due to the economic crisis and constant wars, there was an acute shortage of precious metals for making money, so the royal courts were looking for new trading markets, and, most importantly, places where there was a lot of cheap gold. This is how we learned about the existence of America and Australia!

Golden Mask (Thailand)

Initially, humanity used gold only for making jewelry and luxury items, but gradually began to serve as a means of exchange, i.e. began to perform the function of money. Gold was used in this capacity as early as 1500 BC. e. in China and Egypt. In the state of Lydia (the territory of modern Turkey), which had huge deposits of gold, gold coins began to be minted for the first time. The amount of gold in this state exceeded all the reserves of this metal available at that time in other states, so much so that the name of the Lydian king Croesus became a proverb and became synonymous with untold wealth. They say “Rich as Croesus.”
In the Middle Ages and later, the main source of gold was South America. But at the beginning of the 19th century, large deposits of gold were discovered in the Urals and Siberia, so for several decades Russia took first place in its production. Later, rich deposits were discovered in Australia and South Africa. Thus, there was a sharp increase in gold production. Until this time, along with gold, silver was used from precious metals to produce coins. But the influx of gold from the above-mentioned countries ensured the displacement of silver. Therefore, by the beginning of the 20th century, gold had established itself as the standard. Gold itself is rarely used as a material for coins, because... it is very soft and ductile (1 gram of gold can be stretched over 1 km), and therefore quickly abraded; it is mainly used in the form of alloys that increase the hardness of the material. But at first, coins were minted from pure gold and one of the ways to check a coin was to try it “by tooth”, the coin was clamped with teeth, if a decent trace remained, it was believed that the coin was not counterfeit.

Distribution of gold in nature

Gold is not very common on our planet, but it is not rare either; its content in the lithosphere is about 4.3 10 -7%, and one liter of sea water contains about 4 10 -9 g. A certain amount of gold is found in soil, from where plants receive it. Corn is an excellent source of natural gold for human nutrition; this plant has the ability to concentrate it in itself. Mining gold is an extremely difficult task, which is why it has such a high price. As geologists say, “gold loves solitude,” because... most often it is found in the form of nuggets, i.e. it is found in the ore in its pure form. Only in extremely rare cases are compounds of gold found with bismuth and selenium. A very small amount of it is found in igneous rocks and hardened lava. But extracting gold from them requires even more work, and its content is very low. Therefore, the method of extraction from igneous rocks is not used due to its unprofitability.
The main gold reserves are concentrated in Russia, South Africa and Canada.

Chemical properties of gold

Most often, gold has a valence of +1 or +3. This is a metal that is very resistant to aggressive influences. Gold is completely unaffected by oxidation, i.e. oxygen at normal conditions has no effect on him. However, if you heat gold above 100° C, a very thin oxide film is formed on its surface, which does not disappear even when cooled. At a temperature of 20 °C the film thickness is approximately 0.000001 mm. Sulfur, phosphorus, hydrogen and nitrogen do not react with gold.
Gold is not affected by acids. But only if they act on him separately. The only pure acid in which gold can be dissolved is hot concentrated selenic acid H 2 SeO 4 . At room temperature, the noble metal dissolves in the so-called “regia vodka”, i.e. mixtures of “nitric acid + hydrochloric acid”. Also, under normal conditions, gold is very susceptible to solutions of potassium iodide and iodine.

Applications of gold

Since ancient times, gold has been used in jewelry, as an object of luxury and power. Thanks to its exceptional ductility and malleability, jewelers can create real works of art from this metal. In industry, gold is used in the form of alloys with other metals. Firstly, this increases the strength of the alloy, and secondly, it reduces the cost of production. The gold content in an alloy is called “fineness,” which is expressed by some kind of whole standard number. For example, a kilogram of 750-carat alloy contains 750 grams of gold. The remaining 250 are other impurities. Therefore, the higher the fineness, the higher the gold content in the alloy. There is a standard for this content: 375, 500, 585, 750, 900, 916, 958 samples are used.

Do you know that?

In order to make one gold ring, you need to process a ton of gold ore!

In other industries, gold is used for various purposes in chemical and petrochemical production, energy and electronics, aviation and space technology. This noble metal is used wherever corrosion is under no circumstances desired. It has also been widely used in medicine since time immemorial due to its resistance to oxidation. Mummies with gold crowns of teeth have been found in Egyptian tombs. Currently, high-strength gold alloys are used for dentures and crowns. In addition, gold is used in pharmacology. Here, various precious metal compounds are used, which are included both in the composition of the preparations and are used separately. Gold threads are used in cosmetology, where they help rejuvenate the skin.

Do you know that?

In the Japanese city of Suwa there is a plant where gold is extracted from the ashes left after burning industrial waste! Moreover, in this ash its content is greater than in any gold-bearing mine. This fact is explained by the fact that there are a lot of factories in the city that produce electronics, in which this noble metal is widely used.

Summarize. Gold has retained its investment, industrial, jewelry and medical purposes for several millennia, and this trend is unlikely to be interrupted in the foreseeable future. Gold will always be the personification of luxury and wealth!

gold in the chemical periodic table and got the best answer

Answer from Anastasia[guru]
Gold is the 79th element of the periodic table of elements, a noble metal of yellow color.
Gold is the most inert metal, standing in the series of stresses to the right of all other metals; under normal conditions, it does not react with most acids and does not form oxides, due to which it was classified as a noble metal, in contrast to ordinary metals, which are easily destroyed under the influence of environment. Then the ability of aqua regia to dissolve gold was discovered, which shook confidence in its inertness.
Of the pure acids, gold dissolves only in hot concentrated selenic acid:
2Au + 6H2SeO4 = Au2(SeO4)3 + 3H2SeO3 + 3H2O
Gold reacts relatively easily with oxygen and other oxidizing agents with the participation of complexing agents. Thus, in aqueous solutions of cyanides with access to oxygen, gold dissolves, forming cyanoaurates:
4Au + 8CN− + 2H2O + O2 → 4− + 4 OH−
In the case of a reaction with chlorine, the possibility of complex formation also significantly facilitates the course of the reaction: if gold reacts with dry chlorine at ~200 ° C to form gold (III) chloride, then in an aqueous solution (regia vodka) gold dissolves with the formation of chloraurate ion already at room temperature temperature:
2Au + 3Cl2 + 2Cl− → 2−
Gold easily reacts with liquid bromine and its solutions in water and organic solvents, giving tribromide AuBr3.
Gold reacts with fluorine in the temperature range 300−400°C; at lower temperatures the reaction does not occur, and at higher temperatures gold fluorides decompose.
Gold also dissolves in mercury, effectively forming a low-melting alloy (amalgam).
Gold / Aurum (Au),Gold,Or
Atomic number 79
Appearance Soft viscous
malleable yellow
metal
Properties of the atom
Atomic mass
(molar mass) 196.96654 a. e.m. (g/mol)
Atomic radius 146 pm
Ionization energy
(first electron) 889.3 (9.22) kJ/mol (eV)
Electronic configuration 4f14 5d10 6s

Answer from 2 answers[guru]

Hello! Here is a selection of topics with answers to your question: gold in the chemical periodic table

As follows from the above, gold has a number of unique properties: among metals it has the highest electronegativity, the highest electron affinity, the highest orbital density, malleability and ductility. This is an element among metals, closest to non-metals in its chemical properties, and at the same time in its physical properties- typical metal.

The uniqueness of gold as a chemical element becomes largely clear upon careful consideration and analysis of its location in the periodic table of elements by D.I. Mendeleev (unexpanded version): having serial number 79, it occupies an exceptional position - located in the very bottom left corner of the table (Fig. 2). Below and slightly to the right of gold there is only one element - francium, with serial number 87, but it is in natural conditions practically not fixed. Francium is the rarest element from the group of rare ones. Of all the chemical elements (excluding transuranic elements), it is the most unstable. The half-life of its most stable isotope is only 22 minutes. Francium is obtained in minute quantities that cannot be weighed artificially as a result of nuclear reactions, including the irradiation (bombardment) of gold with accelerated multiply charged ions or high-energy protons. According to calculations, out of 5976 * 10-18 tons of earthly matter, francium accounts for a little more than 500 g.
Gold, being the closest upper neighbor of francium in the first group of elements, is also characterized by a correspondingly extremely low content in the earth’s crust. Although its Clarke is much higher in comparison with France, it nevertheless remains very low - about 4 mg/t. Clarke of all other metals located in the D.I. table. France is closer to Mendeleev, i.e., with a serial number less than 87, much higher - 20-1000 times. At the same time, the lowest clarks have the metals that are the closest neighbors of gold in the table - silver, platinum and mercury, located respectively in the same subgroup - above gold and to the left and right of it - in the same row with gold. It is the clarks of these three metals that are approximately 20 times higher than the clarks of gold. All other metals, including thallium, lead and bismuth, have clarke values ​​2-3 or more orders of magnitude greater than gold.

This explains the relatively rare occurrence of gold deposits and, most importantly, the relatively low gold content in them. Thus, in comparison with molybdenum, tungsten and tin, the industrial gold content is on average a thousand times less, in comparison with lead and zinc - ten thousand times. This, first of all, as well as the complexity of the geological structure of gold deposits and the usually extremely uneven distribution of metals in them, explains the high prices for gold and its use as a generally recognized currency metal.

With large reserves, gold deposits can be profitable for exploitation using the simplest flotation-gravity enrichment schemes even at contents of 2-3 g/t. Under favorable mining and technical conditions and technological properties of ores suitable for selective leaching of metal, deposits with lower contents of 0.5-1.5 g/t are mined. With further technical progress, objects with lower concentrations of gold will undoubtedly be brought into operation, especially during complex ore processing.

In light of the above, gold deposits are rare formations in which the concentration of the main useful component in a certain volume increases compared to the usual clarke background by at least hundreds to thousands of times due to an extremely favorable combination of various factors for ore concentration - geochemical, structural and tectonic , paleohydrological, metamorphic or igneous. Successful prospecting and evaluation of gold deposits obviously requires great skill, skillful use and knowledge of all these factors.

In the periodic table of elements D.I. Mendeleev gold is in the same group I with the alkali metals - Na, K, Rb, Cs - and as the latter is a typical metal in its physical properties. However, in terms of its position in the group, it differs significantly from the alkali metals: it is located not in the main, but in the secondary subgroup, together with copper and silver. Accordingly, its chemical properties are significantly different. This is due to the fact that the outer electron of a gold atom (like copper and silver) is much closer to the nucleus and, therefore, is more strongly attracted to it. For the same reason, gold ions are much easier to reduce. i.e., they do not give away, but gain electrons. Differences in the structure of the electronic layers of elements of the main and secondary subgroups also cause significant differences in the valency of gold and alkali metals.

Based on the position in the table D.I. Mendeleev also makes clear the exceptional diversity of geochemical properties of gold: it is simultaneously a siderophile, chalcophile and lithophile element. It also exhibits sharply halogenophilic, hydrophilic and especially biophilic properties. The atmospheric (neutral) properties of gold, which determine its “native” nature, are also well expressed. All this determines the “cosmopolitanism” of gold - the ability to form industrial concentrations as a result of very diverse reactions and geological processes. It was not by chance that researchers previously classified gold according to geochemical characteristics into various classes or groups: V.M. Goldshmidt - to the chalcophile class, V.I. Vernadsky - to noble metals, E. Sadetsky-Kardosh - to the siderophilic group, American researchers - to biophilic elements, A.I. Perelman - to chalcophile metals, etc.

Siderophilic properties of gold are well known and quite understandable based on its location in the periodic table of elements: in it, gold is adjacent to platinum (the serial number of platinum is 78, gold is 79) - an element of group VIII with pronounced siderophilic properties. For the first time, the siderophilic properties of gold were demonstrated in detail by Yu.G. Shcherbakov, who devoted detailed research to this issue. Gold, both in a dispersed state and in ore concentrations, clearly gravitates towards dark-colored and ore minerals and rocks (sedimentary, metamorphic, igneous) containing significant quantities of iron. Its Clarke for iron-containing minerals and rocks is clearly higher than for weakly iron-bearing and iron-free ones. The work of recent years on assessing the gold content of ferruginous quartzites turned out to be especially highly productive. It has been established that they almost always contain significant concentrations of syngenetic gold and are newly formed, regenerated, and often cost-effective for extraction. Gold deposits in ferruginous quartzites, primarily Early Precambrian (AR-PR1), currently occupy one of the important places in gold mining in many foreign countries. In this regard, gold deposits of the gold-jaspilite formation have been identified. They are often quite large in reserves. especially the carbonate-sulfide facies. Typical examples are the Morro Velho, Passagem and Panococ deposits on the Brazilian Shield, Copperhead and Hill-50 on the Western Australian Shield, and Central Patricia on the Canadian Shield.

On the territory of Russia, the gold content of ferruginous quartzites has been poorly or very poorly studied, and a relatively small amount of prospecting work has been carried out. Elevated gold contents were established in ferruginous quartzites of Krivoy Rog and the Mikhailovsky mine of the Kursk magnetic anomaly (up to 1.5 g/t in individual samples, rarely higher), as well as in the south of the Siberian platform in Yakutia (Lemochinsky site) and in the Amur region (Khorogochi site ), where the contents have so far turned out to be low, but in some rare samples they reach 10-15 g/t. The ferruginous quartzites of the Bureya massif (Kimkanskoe deposit, etc.) were not specifically assessed for gold at all. In several selected ore samples, elevated gold contents were not found. However, in the ferruginous quartzites of the neighboring Heilongshian Province of China, similar in age, a spent gold deposit is known with an average gold content of about 1.5 g/t. Higher contents are typical for iron hydroxides, magnetite and iron sulfides. Increased gold contents (up to 1.4 g/t) were also noted in the metal phase of iron meteorites.

In the developed foreign deposits of the gold-jaspilite formation, the average gold content is very different - from 1.5 to 10-15 g/t.

Chalcophilic the properties of gold are less noticeable based on its position in the periodic table, and it is no coincidence that the relationship of gold directly with sulfur is often contradictory. The association of gold with iron-containing sulfides is more typical, since conditions that are simultaneously high in iron and sulfur (sulfides) are most preferable for ore formation. Therefore, it is better to characterize gold as a siderochalcophile element. Directly in the periodic table, the relationship between gold and sulfur is expressed by the nature of the properties of its closest “neighbors” vertically and horizontally - silver and mercury. Both of them are typical chalcophiles. The connection between gold and sulfides, which has long been taken into account when searching for and predicting gold deposits, is also not accidental.

Halogenophilic The properties of gold have long been known and are used in its dissolution. However, when formally examining the location of gold in the periodic table, they are not visible. Fluorine, chlorine, bromine, and iodine are spatially significantly removed from gold. As a reflection of this, the absence of gold minerals containing halogens is characteristic. Gold halides are the most easily soluble gold compounds. In geological formations, the close connection between gold and fluorine appears quite often, but is hidden. As already noted, the presence of fluorapatite in gold deposits is a common occurrence. Cases of correlation with fluorine have been established.

Biostrong The (organophilic) properties of gold are intensely expressed and manifest themselves in its close connection with various organic formations. Characterized by the presence of organometallic compounds. The increasing importance of gold in the life activity of various plant and animal organisms is being revealed. Carbonaceous strata are the generators of the largest gold deposits in terms of reserves.

Directly from the periodic table, the important role of carbon in the geochemistry of gold is also not particularly noticeable. However, it becomes understandable and, moreover, it can be predicted if we take into account the geochemical properties of carbon and gold and the ability of various gold compounds to be easily reduced by carbon.

Lithophilic The properties of gold are, as a rule, not expressed. Its close association with quartz is determined, essentially, not by chemical, but by crystallophysical and crystallochemical properties of gold and silica gel, the increased ability of the latter to capture, transport and retain colloidal gold and hydroxide compounds of its type Au(OH) and Au(OH)3.

Hydrophilic properties are typical for gold and follow from its position in group I of the periodic table. They manifest themselves in its increased solubility in water, which has been established experimentally. Several forms of gold can be simultaneously present in the dissolved state - cationic, anionic and colloidal, as well as various hydroxo complexes. Their role in ore formation can be very significant - both in hypogene and surface conditions.

The atmophilic (neutral) properties of gold arise from the “nobility” of gold as a chemical element and are decisive in understanding its geochemistry, conditions of concentrated precipitation and distribution in various rocks and minerals. They also manifest themselves in the high volatility of gold. In various rocks and minerals, gold is overwhelmingly present in the form of electrically neutral particles of various sizes - from the smallest, finely dispersed to large nuggets weighing several kilograms.