Completed by: student of group SP - 00 - D1 Ivanov Sergey Tikhonovich

Checked by: Egorov S.N.

Volgodonsk

In connection with the rapid development of communications technology, electronic, aviation, space and other industries, interest in gold has grown significantly. Currently, a large number of new gold alloys have been developed, as well as technological processes for applying gold plating and obtaining multilayer materials.

The prevalence of gold in nature

The earth's crust contains 20 times less gold than silver and 200 times less than mercury. The uneven distribution of gold in different parts of the earth's crust makes it difficult to study its geochemical features. The seas and oceans contain about 10 billion tons of gold. About the same amount of gold is contained in river and ground waters.

Increased gold content is found in the waters of springs and rivers flowing in gold-bearing areas. In nature, gold is mainly found in its native form and is a mineral that is a solid solution of silver in gold, containing up to 43% Ag, with admixtures of copper, iron, lead, less often bismuth, mercury, platinum, manganese and other elements. In addition, gold is found in the form of natural amalgams, as well as chemical compounds - solenides and tellurides. By particle size, native gold is divided into fine (1 - 5 microns), dusty (5 - 50 microns), fine (0.05 - 2 mm) and coarse (more than 2 mm). Particles weighing more than 5 g are nuggets. The largest nuggets - "Halterman Plate" (285 kg) and "The Desired Stranger" (71 kg) were found in Australia. Nugget finds are known in many regions of the Urals, Siberia, Yakutia and Kolyma. Native gold is concentrated in hydrothermal deposits.

Gold deposits are divided into primary and loose. Gold deposits were formed in different geological epochs at different depths - from tens of meters to 4 - 5 km from the earth's surface. Primary deposits are represented by veins, systems of veins, deposits and zones of veinlet - disseminated ores ranging from tens to thousands of meters. During a long period of the history of the earth, the mountains were destroyed and the water carried away everything that did not dissolve in the rivers. At the same time, heavy minerals were separated from the lungs and accumulated in places where the flow rate is low. This is how placer deposits were formed with a concentration of relatively large gold. As a rule, industrial placers are formed relatively close to primary deposits. A certain part of microscopic particles of gold remains in placers, however, due to the impossibility of its extraction, it has no practical value. Part of microscopic and colloidal particles of gold is carried away by water sources to seas, oceans and lakes, where it is dispersed in the form of the finest suspensions or is in silty sediments. Thus, as a result of the action of erosion processes, most of the gold is irretrievably lost.

Chemical properties

Despite the fact that gold in the periodic system of D.I.Mendeleev is in the same group with silver and copper, its chemical properties are much closer to the chemical properties of platinum group metals. The electrode potential of the Au - Au (111) pair is - 1.5 V. Due to such a high value, diluted and concentrated HCI, HNO, HSO do not act on gold. However, in HCI, it dissolves in the presence of oxidizing agents such as magnesium dioxide, ferric chloride and copper, as well as under high pressure and high temperature in the presence of oxygen. Gold also dissolves easily in a mixture of HCI and HNO (aqua regia). Chemically, gold is an inactive metal. In air, it does not change, even with strong heating. Gold readily dissolves in chlorine water and in aerated solutions of alkali metal cyanides. Mercury also dissolves gold, forming an amalgam, which becomes solid at more than 15% gold. There are two known series of gold compounds corresponding to the oxidation states +1 and +3. So, gold forms two oxides - gold oxide(1), or gold oxide, AuO and gold oxide(111), or gold oxide, AuO. Compounds in which gold has an oxidation state of +3 are more stable. Gold compounds are easily reduced to metal. Reducing agents can be hydrogen under high pressure, many metals in the range of voltages up to gold, hydrogen peroxide, two tin chloride, iron sulfate, titanium trichloride, lead oxide, manganese dioxide, alkali and alkaline earth metal peroxides. Various organic substances are also used to restore gold: formic and oxalic acids, hydroquinone, hydrazine, metol, acetylene, etc. Gold is characterized by the ability to form complexes with oxygen and sulfur-containing ligands, ammonia and amines due to the high energy of formation of the corresponding ions. The most common compounds are monovalent and trivalent gold. They are often considered as complex molecules consisting of an equal number of Au (1) and Au (3) atoms. Trivalent gold is a very strong oxidizing agent and forms many stable compounds. Gold combines with chlorine, fluorine, iodine, oxygen, sulfur, tellurium, and selenium.

Physical and mechanical properties

Gold has long been an object of scientific research and belongs to the number of metals, whose properties have been studied deeply enough. The atomic number of gold is 79, the atomic mass is 197.967, and the atomic volume is 10.2 cm / mol. Natural gold is monoisotopic and, under normal conditions, is inert with respect to most organic and inorganic substances. Gold has a face-centered cubic lattice and does not undergo allotropic transformations. Lattice constant a is 4.07855 A at 25 C, which corresponds to a value of 4.0724 A at 20 C. The effect of pressure on the density of gold is shown in the figure:

0 100 200 300 400

Large discrepancies exist as a result of measuring the melting temperature of gold - from 1062.7 to 1067.4 C. As a rule, the melting point of gold is considered to be 1063 C. The heat of sublimation of gold at 25 C is 87.94 kcal. The surface tension of molten gold is 1.134 J / m. The thermal conductivity of gold l at 20 C is 0.743 cal and changes little with increasing temperature. At low temperatures, a maximum of thermal conductivity is observed at 10 K. The temperature coefficient of electrical resistivity at 0 - 100 C is 0.004 C. Irradiation, work hardening and quenching of gold lead, as a result of the formation of lattice defects, to small changes in the lattice parameter and volume of the metal. However, these changes are not very significant, the linear dimensions change only by a few hundredths of a percent. In the process of annealing, a thermal return of properties occurs, the change in which was caused by lattice defects. Pure gold is characterized by a low value of the ultimate strength s - about 13 - 13.3 kgf / mm - and a high value of the relative elongation - about 50% - in the annealed state. The yield point s is also very low, equal to 0.35 kgf / mm. Strengthening during plastic deformation is very insignificant due to the tendency of gold to recrystallize during deformation.

Application of gold in science and technology

For thousands of years, gold has been used for the production of jewelry and coins, and the use of gold for dental prosthetics is known to the ancient Egyptians. The use of gold in the glass industry has been known since the end of the 17th century. Gold foil, and later gold electroplating, was widely used for gilding the domes of church temples. Only the last 40 - 45 years can be attributed to the period of purely technical use of gold. Gold has a unique set of properties that no other metal has. It has the highest resistance to aggressive media, in terms of electrical and thermal conductivity it is second only to silver and copper, the gold core has a large neutron capture cross-section, the ability of gold to reflect infrared rays is close to 100%, in alloys it has catalytic properties. Gold is very technologically advanced, it is easy to make ultra-thin foil and micron wire from it. Gold plating is easily applied to metals and ceramics. Gold is well soldered and pressure welded. This combination of useful properties has led to the widespread use of gold in the most important modern branches of technology: electronics, communications technology, space and aviation technology, chemistry.

It should be noted that 90% of gold is used in electronics in the form of coatings. Electronics and related engineering industries are the main consumers of gold in technology. In this field, gold is widely used for connecting integrated circuits by pressure or ultrasonic welding, contacts of plug connectors, as thin wire conductors, for soldering transistor elements and other purposes. In the latter case, it is especially important that gold forms low-melting eutectics with indium, gallium, silicon and other elements that have a certain type of conductivity. In addition to technological improvements in electronics, for a number of parts and assemblies instead of gold, they began to use palladium, tin coatings, tin-lead alloys and an alloy of 65% Sn + 35% Ni with a gold sublayer. Alloy of tin with nickel has high wear resistance, corrosion resistance, acceptable contact resistance and electrical conductivity. Despite the fact that currently the consumption of gold in electronics is constantly increasing, it is believed that it could be 30% higher, if not for measures aimed at saving gold.

In microelectronics, gold-based pastes with different electrical resistance are widely used. The widespread use of gold and its alloys for contacts of low-current equipment is due to its high electrical and corrosive properties. Silver, platinum and their alloys, when used as contacts switching microcurrents at microvoltage, give much worse results. Silver quickly tarnishes in an atmosphere contaminated with hydrogen sulfide, while platinum polymerizes organic compounds. Gold is free of these shortcomings, and its alloy contacts provide high reliability and long service life. Low vapor pressure gold solders are used to solder vacuum-tight seams of electronic tube parts, as well as to solder assemblies in the aerospace industry.

Alloys of gold with cobalt or chromium are used in measuring technology for temperature control and especially for measurements of low temperatures. In the chemical industry, gold is mainly used for cladding steel pipes for the transport of corrosive substances.

Gold alloys are used in the manufacture of watch cases and nibs for fountain pens. In medicine, not only prosthetic gold alloys are used, but also medicinal preparations containing gold salts for various purposes, for example, in the treatment of tuberculosis. Radioactive gold is used in the treatment of malignant tumors. In scientific research, gold is used to capture slow neutrons. With the help of radioactive isotopes of gold, diffusion processes in metals and alloys are studied.

Gold is used for the metallization of window panes in buildings. During the hot summer months, a significant amount of infrared radiation passes through the glass panes of buildings. Under these circumstances, a thin film (0.13 µm) reflects infrared radiation and the room becomes much cooler. If a current is passed through such glass, it will acquire anti-fog properties. Gold-plated sight glasses of ships, electric locomotives, etc. effective at any time of the year.

Monetary and financial value of gold

Before the advent of coins, bars or rings made of gold, silver or copper served as the means of payment, which led to great inconvenience in trade settlements. The ingots had to be weighed, divided into smaller ones. This served as a decisive precondition for the transition to minting coins.

Most researchers believe that the first gold coin was minted in the 7th century. BC. in Lydia from an alloy containing 73% Au and 27% Ag. A little later, gold coins began to be minted in ancient Greece. In the countries of the Mediterranean and the Middle East, silver coins were in circulation along with gold coins, which indicates the early origin of bimetallism. The value ratio between gold and silver was different depending on the era and the availability of these metals. According to Pliny's testimony, the Romans knocked out the first gold coin in the 3rd century. BC. The word "coin" itself comes from the name of the Roman temple of Juno - Moneta, where the first Roman mint was organized.

At the beginning of the XIX century. a transition to the gold standard is planned in Great Britain, legislatively - at the end of the 18th century, in fact - in 1823. In France, Germany, Russia, Japan and the United States, the transition to a monometallic monetary system was completed in the last quarter of the 19th century. The highest form of the gold standard was the gold coin standard, characterized by free circulation in the internal circulation of gold coins and their free minting, unlimited exchange for paper money at firm parities, free import and export of gold abroad.

Free circulation of gold to the greatest extent met the requirements of the free enterprise system, served the development of international monetary relations, which gradually took shape in the monetary system.

The bulkiness of gold coins and the associated inconvenience and costs during transportation, the gradual wear and tear of coins, and the costs of circulation were the objective reasons for the transition to paper money.

High prices for gold stimulate the development of its substitutes, but it is clear that a universal substitute for gold cannot be found. We can only talk about replacing gold with cheaper material in separate devices, where the working conditions allow it to be done. If we take into account the growth of space programs, then we can expect a significant increase in the technical use of gold. Undoubtedly, if it were not for the specific monetary functions of gold, this metal would be much more widely used in technology at the present time.

15.10.2015

Gold is perhaps the most ancient substance that has been mined since time immemorial. Perhaps this is even the very first metal that our humanity met. Its first mention in India dates back to 2000-1500 BC, where various kinds of jewelry and works of art were made from it. In its native state, they encountered it in the 5th century BC.

Scientists have suggested that the history of distribution began in the Middle East. From here, the metal was supplied to Egypt, where it became a symbol of wealth and luxury. So during the excavation of the tomb, a headdress was found that belonged to the queen of the Sumerian people as far back as 3000 BC. On the wall, at the burial site, there was an image of a craftsman mining gold. Also, the tomb of the well-known Pharaoh Tutankhamun was decorated with multiple gold ornaments.

In those days, it was believed that such objects as a sign of power accompany the deceased kings to another world. All gold made before the 6th century BC it was "dirty" with admixtures of copper, silver, etc., later in Egypt they learned how to extract the purest metal at the deposits in Nubia. This is where the ancient name of gold comes from - noob... Sanskrit word gold translates as yellow, and the Latin name is aurum- refer to the word Aurora, which in translation means Morning dawn.

On the territory of Russia, mines were discovered quite later, since all gold was imported here in the form of money and duties. It was only by the 17th century that metal began to be mined in the province of Arkhangelsk. The beginning of the discovery is considered to be already the 18th century, when the schismatic Markov Erofei found an inconspicuous stone and reported it to the Chancellery of the Management Board of Yekaterinburg factories. At this place, the "Primordial" mine was founded. For the first decade, almost 6,000 kg were mined on it, the work was very hard and subsequently began to be considered a hard labor.

The content of gold in nature is extremely small, it has been proven that it is also contained in water. So, for example, there are up to 5 kg of metal per 1 km 3. Some observatories exploring outer space are able to detect the formation of gold, which, according to the new theory, is formed as a result of the decay of neutron stars. The essence of the theory is as follows - the dust formed as a result of decay, falling into space, accumulates there. It gets to the Earth thanks to asteroids.

Gold nuggets are quite often found in nature in the form of ore, while chemical compounds of gold, on the contrary, are extremely rare. These are mainly tellurides, and gold can also be present in sulfide minerals. The purity of this metal is determined in carats and in samples. The purest gold corresponds to 24 carats (24 parts of the alloy is equal to 24 parts of gold). The sample of 575 is usually read as follows, an alloy of 1000 parts contains 575 gold. Ingots, which are produced by special refining methods for various financial institutions and other important structures, have a fineness of 999.9

Gold is considered the main metal, because of which more than a dozen warriors were launched. Such "golden battles" as the conquest of Babylon by the Persian king, the battle of Alexander the Great for Persia, Caesar's devastating raids on Egypt and Galia are known for certain. Today, gold has remained a currency metal, and its production is also constantly growing.

Gold (English Gold, French Or, German Gold) is one of the seven metals of antiquity. It is generally believed that gold was the first metal that people met in the Stone Age due to its distribution in its native state. The special properties of gold - heaviness, luster, non-oxidizability, malleability, ductility - explain why it began to be used from the most ancient times mainly for the manufacture of jewelry and partly for weapons. Gold objects for various purposes were found by archaeologists in cultural layers dating back to the 4th and even the 5th millennium BC, i.e. to the Neolithic era. In the III and II millennia BC. NS. gold was already widespread in Egypt, Mesopotamia, India, China, since ancient times it was known as a precious metal to the peoples of the American and European continents. The gold, from which the most ancient jewelry is made, is unclean; it contains significant admixtures of silver, copper and other metals. Only in the VI century. BC NS. almost pure gold appeared in Egypt (99.8%). In the era of the Middle Kingdom, the development of the Nubian gold deposits (Nubia, or Ethiopia of antiquity) began. Hence the ancient Egyptian name for gold - nub (Nub). In Mesopotamia, gold mining on a large scale was carried out already in the II millennium BC. NS. The Babylonian name for gold - hure - shu (hurasu) has a distant resemblance to the ancient Greek word (chrysos), which is found in all ancient literary monuments. Perhaps this word comes from the name of the area where the gold could have come from. The ancient Indian ayas (gold) was later used in other languages ​​to designate copper, which may indicate the spread of counterfeit gold in antiquity. Since ancient times, gold has been compared with the sun, it has been called the solar metal or simply the sun (Sol). In Egyptian Hellenistic literature and among alchemists, the symbol of gold is a circle with a dot in the middle, i.e. the same as the sun symbol. Sometimes in Greek alchemical literature there is a symbol in the form of a circle with the image of a ray associated with it.

Gold, as the most precious metal, has long served as an exchange equivalent in trade, and in this connection, methods of making gold-like copper-based alloys arose. These methods were widely developed and spread and served as the basis for the emergence of alchemy. The main goal of the alchemists was to find ways of converting (transmuting) base metals into gold and silver. European alchemists, following in the footsteps of the Arab, developed a theory of "perfect" or even "super-perfect" gold, the addition of which to a base metal turns the latter into gold. In alchemical literature, there are many names for gold, usually encrypted: zaras, tricor, salt, sun (Sonir), secur (secur), senior, etc. Some of them have Arabic origin, eg al-bahag (joy), hiti (cat droppings), ras (head, principle), su "a (ray), diya (light), alam (peace).

Latin (Etruscan) name for gold aurum (Aurum, ancient ausom) means "yellow". This word compares well with the ancient Roman aurora or ausosa (dawn, eastern country, east). According to Schroeder, the word gold among the peoples of Central Europe also means yellow: in the ancient Germanic language - gulth, gelo, gelva, in Lithuanian - geltas, in Slavic - gold, in Finnish - kulda. Some Siberian peoples call gold altun, the ancient Persians call it zarania (or zar), which is compared with ancient Indian hyrania (more often, however, referring to silver) and ancient Greek (heaven). The Armenian name for gold - oski - stands apart. Slavic gold, or gold, used since ancient times, is undoubtedly associated (contrary to Schroeder) with the most ancient Indo-European Sol (sun), probably as well as Central European Gold (gelb) with Greek (sun).

Such a variety of names for gold testifies to the widespread acquaintance with it of various ancient peoples and tribes and to the crossing of different tribal names. Derivative names of gold compounds, used at the present time, come from the Latin aurum, Russian "gold" and Greek.

The unique chemical properties of gold have given it a special place among the metals used on Earth. Gold has been known to mankind since ancient times. It has been used since ancient times as jewelry, alchemists tried to remove the precious metal from other less noble substances. Currently, the demand for it is only growing. It is used in industry, medicine, technology. In addition, it is purchased by both states and individuals, using it as an investment metal.

Chemical properties of the "king of metals"

The Au sign is used to denote gold. This is an abbreviation for the Latin name of the metal - Aurum. In the periodic system of Mendeleev, it is numbered 79 and is located in group 11. In appearance, it is a yellow metal. Gold is in the same group with copper, silver and X-ray, but its chemical properties are closer to the platinum group metals.

Inertness is a key property of this chemical element, which is possible due to the high value of the electrode potential. Under standard conditions, gold does not interact with anything other than mercury. With it, this chemical element forms an amalgam, which easily decomposes when heated at only 750 degrees Celsius.

The chemical properties of the element are such that other compounds with it are also short-lived. This property is actively used in the extraction of precious metals. The reactivity of gold increases significantly only with intense heating. For example, it can be dissolved in chlorine or bromine water, an alcoholic solution of iodine and, of course, in aqua regia - a mixture of hydrochloric and nitric acid in a certain proportion. The chemical formula for the reaction of such a compound is: 4HCl + HNO 3 + Au = H (AuCl 4) + NO + 2H 2.

The chemistry of gold is such that when heated, it can interact with halogens. To form gold salts, it is necessary to restore this chemical element from an acidic solution. In this case, the salts will not precipitate, but will dissolve into a liquid, forming colloidal solutions of various colors.

Despite the fact that gold does not enter into active chemical reactions with substances, in everyday life you should not allow the interaction of products made of it with mercury, chlorine and iodine. Various household chemicals are also not the best neighbor for precious metal products.

The fact is that an alloy of gold with other metals is used in jewelry, and various substances, interacting with these impurities, can cause irreparable damage to the beauty of the product. If you heat gold above 100 degrees Celsius, then an oxide film with a thickness of one millionth of a millimeter will appear on its surface.

Other features of precious metal

Gold is one of the heaviest metals known. Its density is 19.3 g / cm 3. An ingot weighing 1 kilogram has very small dimensions, 8x4x1.8 centimeters. This is the standard size of a bank gold bar of this weight. It is comparable to the size of a regular credit card, although the bar is slightly thicker.

Heavier than gold, only a few chemical elements: plutonium, osmium, iridium, platinum and rhenium. But their content in the earth's crust, even taken together, is much less than this precious metal. Moreover, plutonium (chemical sign Pu, not to be confused with Pt - this is the sign of platinum) is a radioactive element.

The chemical composition of gold provides its physical properties. So, the main properties of this metal, which make it unique, include:

1. Malleability, ductility, ductility. It is very easy to flatten or pull it out. So, from just one gram of gold, you can get a wire 3 kilometers long, and the area of ​​thin sheets obtained from 1 kilogram will be 530 square meters. Super-thin sheets of gold foil are called "gold leaf". They cover, for example, church domes and the interior decoration of palaces. Due to its ductility, a small amount of yellow metal can cover gigantic areas.
2. Softness. High-quality gold is soft enough to scratch even with a fingernail. That is why canned bars are sold in sealed plastic packaging. If at least one small scratch is noticed on it, then it will be recognized as defective. In order to make gold more durable, other metals are added to it in the manufacture of products. This property has ensured the high popularity of the king of metals in the jewelry industry.
3. High electrical conductivity. Due to this chemical property, gold is highly valued in electrical engineering and industry. Only silver and copper conduct electricity better than it. At the same time, gold hardly heats up: in terms of thermal conductivity, diamond, silver and copper are higher than it. Together with such properties as resistance to oxidation, gold is an ideal substance for the manufacture of semiconductors.
4. Reflection of infrared light. The thinnest, applied to the glass, does not transmit infrared radiation, leaving the visible part of the spectrum. This property is actively used in astronautics, when it is necessary to protect the eyes of astronauts from the harmful effects of the sun. Often, spraying is also used in the mirror system of high-rise buildings in order to reduce the cost of cooling the premises.
5. Resistant to corrosion and oxidation. Ingots, which are stored in accordance with the rules, are practically not subject to any chemical influence even when interacting with air. So the great preservation of gold ensured its high popularity.

Gold mining method

Gold is a fairly rare element on Earth. Its content in the earth's crust is small. It is mainly found in the form of placers in the native state or in the form of ore, and occasionally occurs in the form of minerals. Sometimes gold is mined as an accompanying substance in the development of copper or polymetallic ores.

Mankind knows many ways of extracting this noble metal. The simplest one is elutriation, that is, the separation of gold ore from waste rock using a special process technology. However, this method involves large losses, since the technology is far from perfect. The mechanical method of mining gold ore was replaced by chemistry. Alchemists, and after them chemists, received many ways to isolate the desired metal from the rock, among them the most common:

• amalgamation;
• cyanidation;
• electrolysis.

Electrolysis, discovered in 1896 by E. Volville, has become widespread in industry. Its essence lies in the fact that anodes, consisting of a gold-bearing substance, are placed in a bathroom with a hydrochloric acid solution. A pure gold sheet is used as the cathode. During electrolysis (passing current through the cathode and anode), the desired substance is deposited on the cathode, and all impurities precipitate. Thus, the chemical properties of the precious metal help to obtain it on an industrial scale with virtually no loss.

Alloys with other metals

Noble metal alloys are formed for two purposes:

1. Change the mechanical properties of gold, make it more durable or, on the contrary, more brittle and malleable.
2. Save precious metal stocks.

Various additives to gold are called ligatures. The color and properties of the alloy depend on the chemical formula of its constituents. Thus, silver and copper significantly increase the hardness of the alloy, which makes it possible to use it for making jewelry. But lead, platinum, cadmium, bismuth and some other chemical elements make the alloy more fragile. Despite this, they are often used for the production of the most expensive jewelry, since they significantly change the color of the product. The most common alloys:

• green gold - an alloy of 75% gold, 20% silver and 5% indium;
• white gold is an alloy of gold and platinum (in a ratio of 47: 1) or gold, palladium and silver in a ratio of 15: 4: 1.
• red gold - an alloy of gold (78%) and aluminum (22%);
• in a ratio of 3: 1 (interestingly, an alloy in any other proportion will turn white, and these alloys are called by the general term "electron").

Depending on the amount of gold in the alloy, determine its fineness. It is measured in ppm and denoted by a three-digit number. The amount of the desired metal in each alloy is strictly regulated by the state. In Russia, only 5 samples are officially accepted: 375, 500, 585, 750, 958, 999. Sample numbers mean that this is exactly the number of gold measures per 1000 alloy measures.

In other words, an ingot or product of 585 assay value contains 58.5% gold. Gold of the highest standard, 999, is considered pure. Only chemistry uses it for its own needs, since this metal is too brittle and soft. 750 proof is the most popular in the jewelry industry. Its main components are silver, copper, platinum. The product must have a stamp - a digital sign denoting a sample.

Gold has been known to mankind since ancient times. But in antiquity, it was valued exclusively for its appearance: jewelry sparkling like the sun was a symbol of wealth. Only with the development of chemistry, people realized the real value of this soft metal, and at the moment they are actively using it in such industries as:

• space industry;
• aircraft and shipbuilding;
• medicine;
• Computer techologies;
• other.

These industries have very high requirements for the properties of the material used in them. The importance and prestige of these areas allows the price of gold not only to remain at the same level, but also to slowly creep up. The reason for these properties is the electronic formula of gold, which, as is the case with any other elements, determines its parameters and capabilities.

Which ones can be distinguished? In the brainchild of a Russian genius, the precious metal is number 79, and is designated as Au. Au is short for its Latin name Aurum, which translates to "shining". It is in the 6th period of the 11th group, in the 9th row.

The electronic formula of gold, which is the reason for the valuable - 4f14 5d10 6s1, all of this suggests that gold atoms have a significant molar mass, large weight and are inert in themselves. The outer electrons of such a structure include only 5d106s1.

And it is precisely the inertness of gold that is its most valuable property. Because of it, gold is very resistant to acids, almost never oxidizes, and is incredibly rare as an oxidizing agent.

Therefore, it belongs to the so-called. "Noble" metals. "Noble" metals and gases in chemistry are elements that almost do not react with anything under normal conditions.

Gold can be safely called the noblest metal, since it stands to the right of all its counterparts in a series of tensions.

Chemical properties of gold and its interaction with acids

First, compounds of gold with anything other than mercury are most likely to decay. Mercury, which is an exception in this case, forms an amalgam with gold, which was previously used to make mirrors.

In other cases, connections are short-lived. The inertness of gold in the Middle Ages made alchemists think that this metal is in a kind of "ideal balance", they believed that it does not interact with absolutely anything.

In the 17th century, this idea was destroyed when it was discovered that aqua regia, a mixture of hydrochloric and nitric acids, was capable of corroding gold. The list of acids interacting with gold is as follows:

1. (mixture of 30-35% HCl and 65-70% HNO3), with the formation of hydrochloric acid H [AuCl4].
2. Selenic acid(H2SeO4) at 200 degrees.
3. Perchloric acid(HClO4) at room temperature, with the formation of unstable chlorine oxides and gold perchlorate III.

In addition, gold interacts with halogens. The easiest way is to carry out the reaction with fluorine and chlorine. There is HAuCl4 · 3H2O - hydrochloric acid, which is obtained by evaporating a solution of gold in perchloric acid after passing chlorine vapor through it.

In addition, gold dissolves in chlorine and bromine water, as well as in an alcoholic solution of iodine. It is still unknown whether gold is oxidized by oxygen, because the existence of gold oxides has not yet been proven.

Oxidation states of gold, its bond with halogens and its participation in compounds

The standard oxidation states of gold are 1, 3, 5. Much less common is -1, these are aurides - usually compounds with active metals. For example, sodium auride NaAu or cesium CsAu, which is a semiconductor. They are very diverse in composition. There are rubidium aurides Rb3Au, tetramethylammonium (CH3) 4NAu, and aurides of the composition M3OAu, where M is a metal.

They are especially easy to obtain using compounds where gold acts as an anion, and when heated with alkali metals. The greatest potential for electronic bonds of this element is revealed in reactions with halogens. In general, with the exception of halogens, gold as a chemical element has extremely diverse, but rare bonds.

The most stable oxidation state is +3, at a given oxidation state, gold forms the strongest bond with the anion, in addition, this oxidation state is very easy to achieve through the use of singly charged anions, such as:

• etc.

It should be understood that the more active the anion is in this case, the easier it will be to bond with gold. In addition, there are stable square-planar complexes - which are oxidizing agents. Linear complexes with gold content Au X2, which are less stable, are also oxidizing agents, and gold in them has an oxidation state of +1.

For a long time, chemists believed that the highest oxidation state of gold was +3, but when using krypton difluoride, it was relatively recently possible to obtain gold fluoride in laboratory conditions. This very powerful oxidizing agent contains gold in the +5 oxidation state, and its molecular formula looks like AuF6-.

At the same time, it was noticed that gold +5 compounds are stable only with fluorine. Summarizing the above, you can confidently highlight an interesting tendency towards halogens from the noble metal:

• gold +1 feels great in many compounds;
• gold +3 can also be obtained through a number of reactions, most of which somehow involve halogens;
• gold +5 is unstable if the most aggressive halogen - fluorine - is not combined with it.

Moreover, the bond between gold and fluorine allows you to achieve very unexpected results: gold pentafluoride, when interacting with free, atomic fluorine, leads to the formation of extremely unstable AuF VI and VII, that is, a molecule consisting of a gold atom and six or even seven oxidizing atoms ...

For a metal that was once considered extremely inert, this is a very atypical result. AuF6 dismutes to form AuF5 and AuF7, respectively.

To provoke the reaction of halogens with gold, it is recommended to use gold powder and xenon dihalides in conditions of high humidity. In addition, chemists advise avoiding contact of gold with iodine and mercury in everyday life.

When reduced from an oxidized state, it tends to form colloidal solutions, the color of which varies depending on the percentage of certain elements.

Gold plays an important role in protein organisms, and, accordingly, it is found in organic compounds. Examples are gold ethyldibromide and aurotyloglucose. The first compound is a molecule of gold, oxidized by the combined efforts of ordinary ethyl alcohol and bromine, and in the second case, gold takes part in the structure of one of the types of sugar.

In addition, Crinazole and Auranofin, which also contain gold in their molecules, are used in the treatment of autoimmune diseases. Many gold compounds are toxic and, if accumulated in certain organs, can lead to pathologies.

How do the chemical properties of gold ensure its physical properties?

The high molar mass makes the brilliant metal one of the heaviest elements. Only plutonium, platinum, iridium, osmium, rhenium and several other radioactive elements overtake it in weight. But radioactive elements in the matter of mass are generally special - their atoms, in comparison with the atoms of ordinary elements, are gigantic and very heavy.

The large radius, the ability to form up to 5 covalent bonds and the arrangement of electrons on the last axes of the electronic structure provide the following qualities of the metal:

Plasticity and ductility - the bonds of the atoms of this metal are easily broken at the molecular level, but at the same time they are slowly restored. That is, atoms move with the breaking of bonds in one place and emergence in another. Thanks to this, gold wires can be made of great lengths, and that is why gold leaf exists.

It turns out that this or that element still surpasses gold in one of its useful features. But gold holds its mark precisely because it has a combination of important attributes.

The relationship between the chemical properties of gold and its rarity and mining characteristics

This element almost always occurs in nature in two forms: nuggets or almost microscopic grains in the ore of another metal. At the same time, the common cliche that a nugget glistens and generally at least somehow resembles an ingot should be forgotten. There are several types of nuggets: electrum, palladium gold, cuprous, bismuth.

And in all cases there is a significant percentage of impurities, be it silver, copper, bismuth or palladium. Deposits with grains are called loose. Getting gold is a complex technical and chemical process, the essence of which is the separation of precious metal from ore, ore or rock by means of amalgamation, or the use of a number of reagents.

At the same time, it refers to scattered elements, that is, those that are not found in particularly large deposits and are not found in large pieces of a pure element. This is the result of its low activity and the stability of some compounds with it.