Pure silver is a beautiful white metal, and its Latin name comes from Sanskrit, which means light color.
Silver has high ductility and can be rolled into a transparent foil with a thickness of only 0.00003 cm. Silver particles with a weight of 1 g can be drawn into filaments about two kilometers long.
The thermal conductivity and electrical conductivity of silver are among the best among metals. Silver wire can be used to make physical instrument components with high sensitivity; The joints of important contacts in all kinds of relays are made of silver, and the important parts in the radio system should also be welded with silver as solder. Various automation devices, rockets, submarines, computers, nuclear devices and communication systems all have a large number of contact points. During use, each contact will work millions of times. In order to withstand such strict working requirements, the contact points must be wear-resistant and reliable, and many special technical requirements must be met. These contacts are generally made of silver, and people are very willing to use silver because it can meet all kinds of requirements. If rare earth elements are added to silver, the performance will be better. The contact life made of silver and rare earth elements can be extended several times.
Silver nitrate decomposes into silver when exposed to light or organic matter. Tiny silver is grayish black. This compound is used for silver plating or other silver compounds, and it is also the main raw material for making the photosensitive layer of photographic film. Silver nitrate can converge, sterilize or corrode at different concentrations. The concentrated solution of silver nitrate can corrode the overgrowth of granulation tissue, and its dilute solution can be used to treat conjunctivitis.
Silver oxide is easily soluble in ammonia water, and after the solution is left for a long time, sometimes it will precipitate a strongly explosive black crystal. Silver oxide is used as a colorant in the glass industry.
The photosensitive function of silver bromide is used to make the photosensitive layer of photographic film.
Element Name: Silver
Atomic weight of element: 107.9
Element type: metal
Discovered by: year of discovery:
Discovery process:
In ancient times, people knew about silver. Like gold, silver is a precious metal with a long history of application, which has a history of more than 4,000 years. Because of the unique and excellent characteristics of silver, people give it dual value of money and decoration. The pound and silver dollar used before the liberation of China were silver and copper alloys.
Silvery white, soft and bright, it is a favorite ornament of ethnic minorities, Buddhism and Islam. Silver jewelry is also the first choice gift for newborn babies given by people of all ethnic groups in China. Recently, under the influence of the retro trend of thought, people in Europe and America are wearing light blue turquoise jewelry inlaid with silver, which is easy to oxidize and turn black, bringing people infinite beautiful reverie about ancient civilization. In China, sterling silver jewelry has gradually become the favorite of modern fashionable women. Silver is one of the metals known since ancient times. Silver is more active than gold. Although its abundance in the crust is about 15 times that of gold, it rarely exists in the form of elemental substance, so it was discovered later than gold. In ancient times, people already knew how to mine silver ore, because the amount of silver obtained at that time was very small, which made its value more expensive than gold. During BC 1780 1580, the Egyptian code stipulated that the value of silver was twice that of gold. Even in the17th century, the value of Japanese gold and silver was equal. Silver was first used as decorations and tableware, and later used as currency.
Pure silver is a beautiful white metal. The chemical symbol Ag of silver comes from its Latin name Argentum, which means "light and bright". Its English name is Silver. Silver has high ductility, and can be rolled into a transparent foil with a thickness of only 0.00003cm, and silver particles with a weight of 1g can be drawn into filaments of about 2km. The thermal conductivity and electrical conductivity of silver are among the best among metals.
Elemental silver
Pure silver is a beautiful silvery white metal with good ductility, and its conductivity and heat transfer are the highest among all metals. For example, the conductivity of mercury is 1, that of copper is 57, and that of silver is 59, ranking first. Therefore, silver is often used to make highly sensitive physical instrument components, various automation devices, rockets, submarines, computers, nuclear devices and communication systems. A large number of contacts in all these devices are made of silver. In the process of use, each contact has to work for millions of times, and it must be wear-resistant and reliable, and can withstand strict working requirements. Silver can meet all kinds of requirements.
Among all metals, silver has the best reflection performance on natural light, so silver plays an important role in the mirror industry.
In addition, silver ions can sterilize. Herdsmen in Inner Mongolia, China often use silver bowls to hold horse milk, which can be kept sour for a long time.
The characteristic oxidation number of silver is+1, and its chemical properties are worse than that of copper. At room temperature, even if heated, it will not react with water and oxygen in the air, but it will turn black and lose its silver luster in the air for a long time. This is because silver and H2S in the air synthesize black Ag2S.
4Ag + H2S + O2 = 2Ag2S + 2H2O
Silver can't react with dilute hydrochloric acid or dilute sulfuric acid to release hydrogen, but it can be dissolved in nitric acid or hot concentrated sulfuric acid.
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2Ag+2H2SO4 (concentrated) = = = Ag2SO4+SO2 =+2h2o
Silver reacts slowly with halogen at room temperature and can generate halide when heated.
473,000
2ag+F2 = = = 2agf dark brown.
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2ag+Cl2 = = = = 2agcl white
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2ag+br2 = = = = 2agbr ↓↓↓ yellow
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2ag+I2 = = = = 2agi ↓↓↓ Orange
Silver has a strong affinity for sulfur and can be directly synthesized with sulfur when heated;
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2Ag + S ==== Ag2S
Element description:
Silver white metal. Density:10.5g/cm3. Melting point: 96 1.93℃, boiling point: 22 13℃. Price+1 It is malleable and a metal with good thermal and electrical conductivity. The first ionization energy is 7.576 eV. The chemical properties are stable and have no influence on water and oxygen in the atmosphere; Soluble in dilute nitric acid, hot concentrated sulfuric acid, hydrochloric acid and molten alkali metal hydroxide.
Element source:
The main silver deposit is argentite, followed by amphibole and natural silver. Silver is obtained by heating silver ore with salt and water, then combining with mercury to form a mixture of silver and mercury, and evaporating mercury. Or by leaching silver ore with cyanide alkali and adding lead or zinc to precipitate silver.
Element usage:
Used for making alloys, fluxes, silver foils, silver salts, chemical instruments, etc. , and used to make silver coins and base silver.
Element auxiliary data:
Silver rarely exists in the state of simple substance in nature, but mostly exists in the state of compound, so it was discovered later than gold, and it is generally considered to be 5500-6000 years ago. The general chemistry course in Necrasov also talked about natural silver, and the largest silver nugget found so far weighs 13.5 tons.
Most natural silver alloys with gold, copper, antimony, copper or platinum, and natural gold almost always alloys with a small amount of silver. Amber gold known in ancient China, called ELECTRUM in English, is a natural gold-silver alloy, containing about 20% silver. At first, because people got very little silver, its value was more expensive than gold. In the Egyptian dynasty code between BC 1780- 1580, the value of silver was twice that of gold. Even in the17th century, the value of gold and silver in Japan was equal. Marx said in the critique of political economy: "... and the mining of silver is based on the mine labor force and usually relatively high technological development." Therefore, although silver is not so absolutely scarce, its initial value is relatively greater than the value of gold. "
In the13-14th century, China and Europe have developed the soot blowing method to test gold and silver. This is also a method of separating gold and silver impurities, also known as baking pot metallurgy. In this method, samples of gold and silver to be detected or collected gold and silver are heated in a bowl made of animal ashes, and lead and other impurities form oxides, some of which are blown away by shock waves and some of which penetrate into the ashes, leaving unoxidized gold and silver. In this way, the content and purity of gold and silver in samples or ore gold can be calculated. This method is also used in analytical chemistry so far.
Silver was called platinum in ancient China. In ancient western countries, people used the symbol of the moon to represent silver. In Latin, "silver" is argentum, which comes from the Greek argyros. So the chemical element symbol of silver is Ag.
Moon-like metallic silver
Silver always shines like the moon. The original meaning of silver paper is "bright". In China, silver characters are also commonly used to describe white and shiny things, such as the Milky Way, Ginkgo biloba, whitebait, tremella, screens and so on.
In ancient China, silver was often juxtaposed with gold and copper, which was called "only gold". Gong Yu records that "gold is the only product", which shows that silver was discovered in China as early as the 23rd century BC, that is, more than 4,000 years ago. In nature, silver often exists in the form of pure silver. People once found a piece of pure silver weighing 13.5 tons! In addition, it also exists in the form of chloride and sulfide, and often coexists with minerals such as lead, copper, antimony and arsenic.
The conductivity of silver ranks first among metals. Some pocket radios use silver as a conductor. Silver is also very ductile.
Herdsmen in Inner Mongolia, China often use silver bowls to hold horse milk, which can be preserved for a long time without becoming sour. According to research, this is because a very small amount of silver is dissolved in water in the form of silver ions. Silver ions can kill bacteria, and only 2% of silver ions per liter of water is enough to kill most bacteria. The ancient Egyptians also knew to cover wounds with silver sheets and disinfect them more than two thousand years ago. Nowadays, people wrap the wound door with silver "gauze" woven with silver wire, which is used to treat some skin wounds or intractable ulcers.
Silver is not directly combined with oxygen, and its chemical properties are very stable. Strangely, in February of 1902, on Martini Island near Cuba in Latin America, the silverware turned black in a few days. Later, it was found that the original volcano erupted, and the volcanic gas contained a small amount of hydrogen sulfide, which reacted with silver to generate black silver sulfide. Usually, the air also contains trace amounts of hydrogen sulfide. Therefore, if the silverware is left in the air for a long time, the surface will gradually darken. In addition, the air mixed with trace ozone can directly react with silver to generate black silver oxide. Because of this, the surface of ancient silverware is not as bright as ancient gold. Silver-palladium alloy containing 30% palladium will not turn black when it meets hydrogen sulfide, and is often used to make dentures and decorations.
Silver will not be corroded in dilute hydrochloric acid or dilute sulfuric acid. However, hot concentrated sulfuric acid and concentrated hydrochloric acid can dissolve silver. As for nitric acid, it can dissolve silver more. Silver is alkali-resistant, so silver crucibles are often used when melting potassium hydroxide or sodium hydroxide in chemical laboratories.
Silver, like gold, is also "expensive" among metals and is called "precious metal". In the past, it was only used as money and decorations. Now, silver has three important uses in industry: electroplating, mirror making and photography.
Plating a layer of silver on the surface of some easily rusted metals can prolong the service life and is beautiful. In silver plating, silver is used as the positive electrode and the workpiece is used as the negative electrode (Figure 34). However, silver nitrate solution can not be directly used as electrolyte, because the silver ion concentration is too high, the plating speed is fast, the silver deposition is fast, and the plated silver is loose and easy to fall off. Cyanide is usually added to the electrolyte. Because cyanide ions can form complexes with silver ions, the concentration of silver ions in the solution is reduced, the deposition speed of negative silver is reduced, and the electroplating quality is improved. With the folding out of silver, the concentration of silver ions in the electrolyte decreases. At this time, the silver cyanide complex ions are constantly dissociated and transported to the solution, so that the silver ions in the solution always maintain a certain concentration. But cyanide is very toxic, which is a big disadvantage.
The glass mirror is silvery and shiny, and the back is evenly plated with silver. But this kind of silver is not plated by electroplating, but by "silver mirror reaction": the ammonia solution of silver nitrate and glucose solution are poured together, and glucose is a reducing agent (now the mirror factory also uses formaldehyde and ferrous chloride as reducing agents), which can reduce the silver in silver nitrate into metallic silver and precipitate it on the glass, so a mirror is made. The thermos bottle is also silver and silver-plated.
Silver is of great significance in the manufacture of photographic photosensitive materials. Because photographic paper and film are coated with photosensitizers, which are all silver compounds-silver chloride or silver bromide. These silver compounds are very sensitive to light. They decompose when exposed to light. There is more decomposition in the place with strong light, and less decomposition in the soil fertility with weak light. However, the "image" at this time is only faintly visible and must be revealed to be clear and stable. After development, the unexposed excess silver chloride or silver bromide on the negative is removed. The image on the negative film, contrary to the real scene, is called negative film-where the light is strong, silver chloride or silver bromide is much decomposed, and the color is dark (the black thing on the negative film is extremely fine metallic silver), but the place with weak light appears whiter. When printing a photo, the black and white of the photo is opposite to the negative, so it is consistent with the tone of the real scene. Modern photography technology has been able to take very clear photos in a few tenths to hundreds of seconds under the weak light of matches. Today, the world's silver used for film and photography has reached 150 tons every year.
The most important compound of silver is silver nitrate. In medical treatment, the aqueous solution of silver nitrate is often used as eye drops, because silver ions can strongly kill germs.
The price is generally around 70 yuan/gram, and the purity is 999.