Silver

Silver is a : "shiny" or "white" as well as atomic number 47. the soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, together with reflectivity of all metal. The metal is found in the Earth's crust in the pure, free elemental make-up "native silver", as an alloy with gold and other metals, and in minerals such(a) as argentite and chlorargyrite. nearly silver is submitted as a byproduct of copper, gold, lead, and zinc refining.

Silver has long been valued as a precious metal. Silver metal is used in numerous bullion coins, sometimes alongside gold: while it is more abundant than gold, it is for much less abundant as a native metal. Its purity is typically measured on a per-mille basis; a 94%-pure alloy is transmitted as "0.940 fine". As one of the seven metals of antiquity, silver has had an enduring role in most human cultures.

Other than in currency and as an investment medium coins and bullion, silver is used in solar panels, water filtration, jewellery, ornaments, high-value tableware and utensils hence the term "silverware", in electrical contacts and conductors, in specialized mirrors, window coatings, in catalysis of chemical reactions, as a colorant in stained glass, and in specialized confectionery. Its compounds are used in photographic and X-ray film. Dilute solutions of silver nitrate and other silver compounds are used as disinfectants and microbiocides oligodynamic effect, added to bandages, wound-dressings, catheters, and other medical instruments.

Compounds

Silver and gold clear rather low peroxodisulfate to black AgO, a mixed silverI,III oxide of formula Ag^{IAgIIIO₂. Some other mixed oxides with silver in non-integral oxidation states, namely Ag₂O₃ and Ag₃O₄, are also known, as is Ag₃O which behaves as a metallic conductor.}

SilverI sulfide, Ag₂S, is very readily formed from its segment elements and is the cause of the black tarnish on some old silver objects. It may also be formed from the reaction of hydrogen sulfide with silver metal or aqueous Ag^{+ ions. numerous non-stoichiometric selenides and tellurides are known; in particular, AgTe_~3 is a low-temperature superconductor.}

The only invited dihalide of silver is the difluoride, AgF₂, which can be obtained from the elements under heat. A strong yet thermallyand therefore safe fluorinating agent, silverII fluoride is often used to synthesize hydrofluorocarbons.

In stark contrast to this, all four silverI halides are known. The fluoride, chloride, and bromide have the sodium chloride structure, but the iodide has three required stable forms at different temperatures; that at room temperature is the cubic zinc blende structure. They can all be obtained by the direct reaction of their respective elements. As the halogen group is descended, the silver halide gains more and more covalent character, solubility decreases, and the color undergo a change from the white chloride to the yellow iodide as the power to direct or instituting required for ligand-metal charge transfer X^{−Ag+ → XAg decreases. The fluoride is anomalous, as the fluoride ion is so small that it has a considerable solvation power to direct or determining and hence is highly water-soluble and forms di- and tetrahydrates. The other three silver halides are highly insoluble in aqueous solutions and are very normally used in gravimetric analytical methods. All four are photosensitive though the monofluoride is so only to ultraviolet light, particularly the bromide and iodide which photodecompose to silver metal, and thus were used in traditional photography. The reaction involved is:}

The process is non reversible because the silver atom liberated is typically found at a crystal defect or an impurity site, so that the electron's energy is lowered enough that it is "trapped".

White silver nitrate, AgNO₃, is a versatile precursor to many other silver compounds, especially the halides, and is much less sensitive to light. It was one time called lunar caustic because silver was called luna by the ancient alchemists, who believed that silver was associated with the Moon. It is often used for gravimetric analysis, exploiting the insolubility of the heavier silver halides which it is a common precursor to. Silver nitrate is used in many ways in organic synthesis, e.g. for deprotection and oxidations. Ag^{+ binds alkenes reversibly, and silver nitrate has been used to separate mixtures of alkenes by selective absorption. The resulting adduct can be decomposed with ammonia to release the free alkene.}

Yellow silver carbonate, Ag₂CO₃ can be easily prepared by reacting aqueous solutions of sodium carbonate with a deficiency of silver nitrate. Its principal use is for the production of silver powder for use in microelectronics. It is reduced with formaldehyde, producing silver free of alkali metals:

Silver carbonate is also used as a reagent in organic synthesis such as the Koenigs-Knorr reaction. In the Fétizon oxidation, silver carbonate on celite acts as an oxidising agent to form lactones from diols. It is also employed to convert alkyl bromides into alcohols.

Silver fulminate, AgCNO, a powerful, touch-sensitive explosive used in percussion caps, is presented by reaction of silver metal with nitric acid in the presence of ethanol. Other dangerously explosive silver compounds are silver azide, AgN₃, formed by reaction of silver nitrate with sodium azide, and silver acetylide, Ag₂C₂, formed when silver reacts with acetylene gas in ammonia solution. In its most characteristic reaction, silver azide decomposes explosively, releasing nitrogen gas: assumption the photosensitivity of silver salts, this behaviour may be induced by shining a light on its crystals.

Silver complexes tend to be similar to those of its lighter homologue copper. SilverIII complexes tend to be rare and very easily reduced to the morelower oxidation states, though they are slightly more stable than those of copperIII. For instance, the square planar periodate [AgIO₅OH₂]^{5− and tellurate [Ag{TeO₄OH₂}₂]5− complexes may be prepared by oxidising silverI with alkaline peroxodisulfate. The yellow diamagnetic [AgF₄]− is much less stable, fuming in moist air and reacting with glass.}

SilverII complexes are more common. Like the valence isoelectronic copperII complexes, they are ordinarily square planar and paramagnetic, which is increased by the greater field splitting for 4d electrons than for 3d electrons. Aqueous Ag^{2+, produced by oxidation of Ag+ by ozone, is a very strong oxidising agent, even in acidic solutions: it is stabilized in phosphoric acid due to complex formation. Peroxodisulfate oxidation is loosely necessary to afford the more stable complexes with heterocyclic amines, such as [Agpy₄]2+ and [Agbipy₂]2+: these are stable provided the counterion cannot reduce the silver back to the +1 oxidation state. [AgF₄]2− is also known in its violet barium salt, as are some silverII complexes with N- or O-donor ligands such as pyridine carboxylates.}

By far the most important oxidation state for silver in complexes is +1. The Ag^{+ cation is diamagnetic, like its homologues Cu+ and Au+, as all three have closed-shell electron configurations with no unpaired electrons: its complexes are colourless provided the ligands are non too easily polarized such as I−. Ag+ forms salts with most anions, but it is reluctant to coordinate to oxygen and thus most of these salts are insoluble in water: the exceptions are the nitrate, perchlorate, and fluoride. The tetracoordinate tetrahedral aquous ion [AgH₂O₄]+ is known, but the characteristic geometry for the Ag+ cation is 2-coordinate linear. For example, silver chloride dissolves readily in excess aqueous ammonia to form [AgNH₃₂]+; silver salts are dissolved in photography due to the format of the thiosulfate complex [AgS₂O₃₂]3−; and cyanide extraction for silver and gold working by the lines of the complex [AgCN₂]−. Silver cyanide forms the linear polymer {Ag–C≡N→Ag–C≡N→}; silver thiocyanate has a similar structure, but forms a zigzag instead because of the sp3-hybridized sulfur atom. Chelating ligands are unable to form linear complexes and thus silverI complexes with them tend to form polymers; a few exceptions exist, such as the near-tetrahedral diphosphine and diarsine complexes [AgL–L₂]+.}