Silver

For other uses, see the chemical element.

Silver, ₄₇Ag

Silver
Appearance	lustrous white metal
Standard atomic weight Ar°(Ag)
	107.8682±0.0002 107.87±0.01 (abridged)
Silver in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Cu ↑ Ag ↓ Au palladium ← silver → cadmium
Atomic number (Z)	47
Group	group 11
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d10 5s1
Electrons per shell	2, 8, 18, 18, 1
Physical properties
Phase at STP	solid
Melting point	1234.93 K ​(961.78 °C, ​1763.2 °F)
Boiling point	2435 K ​(2162 °C, ​3924 °F)
Density (at 20° C)	10.503 g/cm3
when liquid (at m.p.)	9.320 g/cm3
Heat of fusion	11.28 kJ/mol
Heat of vaporization	254 kJ/mol
Molar heat capacity	25.350 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1283 1413 1575 1782 2055 2433
Atomic properties
Oxidation states	−2, −1, 0, +1, +2, +3 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.93
Ionization energies	1st: 731.0 kJ/mol 2nd: 2070 kJ/mol 3rd: 3361 kJ/mol
Atomic radius	empirical: 144 pm
Covalent radius	145±5 pm
Van der Waals radius	172 pm
Spectral lines of silver
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered cubic (fcc) (cF4)
Lattice constant	a = 408.60 pm (at 20 °C)
Thermal expansion	18.92×10−6/K (at 20 °C)
Thermal conductivity	429 W/(m⋅K)
Thermal diffusivity	174 mm2/s (at 300 K)
Electrical resistivity	15.87 nΩ⋅m (at 20 °C)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−19.5×10−6 cm3/mol (296 K)
Young's modulus	83 GPa
Shear modulus	30 GPa
Bulk modulus	100 GPa
Speed of sound thin rod	2680 m/s (at r.t.)
Poisson ratio	0.37
Mohs hardness	2.5
Vickers hardness	251 MPa
Brinell hardness	206–250 MPa
CAS Number	7440-22-4
History
Discovery	before 5000 BC
Symbol	"Ag": from Latin argentum
Isotopes of silver
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 105Ag synth 41.3 d ε 105Pd γ – 106mAg synth 8.28 d ε 106Pd γ – 107Ag 51.8% stable 108mAg synth 439 y ε 108Pd IT 108Ag γ – 109Ag 48.2% stable 110m2Ag synth 249.86 d β− 110Cd γ – 111Ag synth 7.43 d β− 111Cd γ –

Silver ({{

Characteristics

A nugget of silver

Silver is a very ductile and malleable (slightly harder than gold) monovalent coinage metal with a brilliant white metallic

Isotopes

Main article: isotopes of silver

Naturally occurring silver is composed of the two stable isotopes, ¹⁰⁷Ag and ¹⁰⁹Ag, with ¹⁰⁷Ag being the more abundant (51.839% natural abundance). Silver's standard atomic mass is 107.8682(2) u. Twenty-eight radioisotopes have been characterised, the most stable being ¹⁰⁵Ag with a half-life of 41.29 days, ¹¹¹Ag with a half-life of 7.45 days, and ¹¹²Ag with a half-life of 3.13 hours.

All of the remaining radioactive isotopes A major use of silver is as a precious metal, and it has long been used for making high-value objects reflecting the wealth and status of the owner.

Jewellery and silverware are traditionally made from sterling silver (standard silver), an alloy of 92.5% silver with 7.5% copper. In the United States, only an alloy consisting of at least 92.5% fine silver can be marketed as "silver". Sterling silver is harder than pure silver, and has a lower melting point (893 °C) than either pure silver or pure copper. Britannia silver is an alternative hallmark-quality standard containing 95.8% silver, often used to make silver tableware and wrought plate. With the addition of germanium, the patented modified alloy Argentium Sterling Silver is formed, with improved properties including resistance to firescale.

Sterling silver jewelry is often plated with a thin coat of .999 fine silver to give the item a shiny finish. This process is called "flashing". Silver jewelry can also be plated with rhodium (for a bright, shiny look) or gold.

Silver is used in medals, deno=== In photography and electronics === Photography used 24% of the silver consumed in 2001 in the form of silver nitrate and silver halides, while 33% was used in jewelry, 40% for industrial uses, and only 3% for coins and medals. However its use in photography is dramatically declining because of the switch to digital technology.

Some electrical and electronic products use silver for its superior conductivity, even when tarnished. For example, printed circuits are made using silver paints, and computer keyboards use silver electrical contacts. Some high-end audio hardware (DACs, preamplifiers, etc.) are fully silver-wired, which is believed to cause the least loss of quality in the signal. Silver cadmium oxide is used in high voltage contacts because it can withstand arcing.

File:Silver (mined)2.PNG

Silver output in 2005

Silver ore (Lincoln cent is shown for scale)

Silver leaf on andesite rock

In solder and brazing

Silver is also used to make solder and brazing alloys, electrical contacts, and high-capacity silver-zinc and silver-cadmium batteries. Silver in a thin layer on top of a bearing material can provide a significant increase in galling resistance and reduce wear under heavy load, particularly against steel.

In mirrors and optics

Mirrors which need superior reflectivity for visible light are made with silver as the reflecting material in a process called silvering, though common mirrors are backed with aluminium. Using a process called sputtering, silver (and sometimes gold) can be applied to glass at various thicknesses, allowing different amounts of light to penetrate. Silver is usually reserved for coatings of specialised optics, and the silvering most often seen in architectural glass and tinted windows on vehicles is produced by sputtered aluminium, which is cheaper and less susceptible to tarnishing and corrosion.

In nuclear reactors

Because silver readily absorbs free neutrons, it is commonly used to make control rods that regulate the fission chain reaction in pressurized water nuclear reactors, generally in the form of an alloy containing 80% silver, 15% indium, and 5% cadmium.

As a catalyst

Silver's catalytic properties make it ideal for use as a catalyst in oxidation reactions, for example, the production of formaldehyde from methanol and air by means of silver screens or crystallites containing a minimum 99.95 weight-percent silver. Silver (upon some suitable support) is probably the only catalyst available today to convert ethylene to ethylene oxide (later hydrolyzed to ethylene glycol, used for making polyesters)—a very important industrial reaction.

Oxygen dissolves in silver relatively easily compared to other gases present in air. Attempts have been made to construct silver membranes of only a few monolayers thickness. Such a membrane could be used to filter pure oxygen from air.

As currency

Silver, in the form of electrum (a gold-silver alloy), was coined to produce money in around 700 BCE by the Lydians. Later, silver was refined and coined in its pure form (see silver coin). Many nations used silver as the basic unit of monetary value (see Silver standard). The words for "silver" and "money" are the same in at least 14 languages. In the modern world, silver bullion has the ISO currency code XAG. The name of the United Kingdom monetary unit "pound" reflects the fact that it originally represented the value of one troy pound of sterling silver. In the 1800s, many nations, such as the United States and Great Britain, switched from silver to a gold standard of monetary value, then in the 20th century to fiat currency.

In medicine

Silver ions and silver compounds show a toxic effect on some bacteria, viruses, algae and fungi, typical for heavy metals like lead or mercury, but without the high toxicity to humans that is normally associated with these other metals. Its germicidal effects kill many microbial organisms in vitro, but testing and standardization of silver products is difficult.

Hippocrates, the father of modern medicine, wrote that silver had beneficial healing and anti-disease properties, and the Phoenicians used to store water, wine, and vinegar in silver bottles to prevent spoiling. In the early 1900s people would put silver dollars in milk bottles to prolong the milk's freshness. Its germicidal effects increase its value in utensils and as jewelery. The exact process of silver's germicidal effect is still not well understood, although theories exist. One of these is the oligodynamic effect, which explains the effect on microorganisms but would not explain antiviral effects.

Silver compounds were used to prevent infection in World War I before the advent of antibiotics. Silver nitrate solution was a standard of care but was largely replaced by silver sulfadiazine cream (SSD Cream), which was generally the "standard of care" for the antibacterial and antibiotic treatment of serious burns until the late 1990s. Now, other options, such as silver-coated dressings (activated silver dressings), are used in addition to SSD cream. However, the evidence for the use of such silver-treated dressings is mixed and although the evidence on if they are effective is promising, it is marred by the poor quality of the trials used to assess these products. Consequently a major systematic review by the Cochrane Collaboration found insufficient evidense to recommend the use of silver-treated dressings to treat infected wounds.

The widespread use of silver went out of fashion with the development of modern antibiotics. However, recently there has been renewed interest in silver as a broad-spectrum antimicrobial. In particular, silver is being used with alginate, a naturally occurring biopolymer derived from seaweed, in a range of products designed to prevent infections as part of wound management procedures, particularly applicable to burn victims. In 2007, AGC Flat Glass Europe introduced the first antibacterial glass to fight hospital-caught infection: it is covered with a thin layer of silver. In addition, Samsung has introduced washing machines with a final rinse containing silver ions to provide several days of antibacterial protection in the clothes. Kohler has introduced a line of toilet seats that have silver ions embedded to kill germs. A company called Thomson Research Associates has begun treating products with Ultra Fresh, an anti-microbial technology involving "proprietary nano-technology to produce the ultra-fine silver particles essential to ease of application and long-term protection." The FDA has recently approved an endotracheal breathing tube with a fine coat of silver for use in mechanical ventilation, after studies found it reduced the risk of ventilator-associated pneumonia.

As a medication

Today, various kinds of silver compounds, or devices to make solutions or colloids containing silver, are sold as remedies for a wide variety of diseases. Although most colloidal silver preparations are harmless, some people using these home-made solutions excessively have developed argyria over a period of months or years. High doses of colloidal sliver can result in coma, pleural edema, and hemolysis.

Silver is widely used in topical gels and impregnated into bandages because of its wide-spectrum antimicrobial activity. The anti-microbial properties of silver stem from the chemical properties of its ionized form, Ag⁺. This ion forms strong molecular bonds with other substances used by bacteria to respire, such as molecules containing sulfur, nitrogen, and oxygen. Once the Ag⁺ ion complexes with these molecules, they are rendered unusable by the bacteria, depriving it of necessary compounds and eventually leading to the bacteria's death.

In food

In India, foods, especially sweets, can be found decorated with a thin layer of silver known as vark. Silver as a food additive is given the E number E174 and is classed as a food coloring. It is used solely for external decoration, such as on chocolate confectionery, in the covering of dragées and the decoration of sugar-coated flour confectionery. In Australia, it is banned as a food additive.

In clothing

Goddess Minerva on a Roman silver plate, 1st century BCE

Silver inhibits the growth of bacteria and fungi. It keeps odour to a minimum and reduces the risk of bacterial and fungal infection. In clothing, the combination of silver and moisture movement (wicking) may help to reduce the harmful effects of prolonged use in active and humid conditions.

Silver is used in clothing in two main forms:

• A form in which silver ions are integrated into the polymer from which yarns are made (a form of nanotechnology)
• A form in which the silver is physically coated onto the yarns.

In both cases the silver prevents the growth of a broad spectrum of bacteria and fungi.

Recorded use of silver to prevent infection dates to ancient Greece and Rome. It was rediscovered in the Middle Ages, where it was used for several purposes, such as to disinfect water and food during storage, and also for the treatment of burns and wounds as wound dressing. In the 19th century, sailors on long ocean voyages would put silver coins in barrels of water and wine to keep the liquid pure. Pioneers in America used the same idea as they made their journey from coast to coast. Silver solutions were approved in the 1920s by the US Food and Drug Administration for use as antibacterial agents. Today, wound dressings containing silver are well established for clinical wound care and have recently been introduced in consumer products such as sticking plasters.

Silversmithery

During the Renaissance and Baroque periods in the sixteenth and seventeenth centuries, Paris was one of the great centers for the creation of lavish silver and gold objects. However, due to the cost of Louis XIV's wars, a large number of them were melted down to pay expenses. Ewers and basins - originally functional objects for washing hands-were used at this time to decorate elaborate buffets on ceremonial occasions, which explains their large proportions and lavish ornamentation.

Ewers and basins were used for both practical and ceremonial purposes. Often, as is the case here, the ewer and basin were created by different silversmiths but formed a set. The designs of silver changed dramatically from the 17th century. In 1625 Henrietta Maria, the daughter of Henri IV and Marie de Medicis of France, was married to Charles I of England. There is no complete description of the silver and gold objects for the wedding, and this ewer and basin are not recorded in the personal inventory of the French-born queen. However, they were most likely commissioned by the French crown to decorate the splendid buffet at the wedding banquet and then given to the couple. Both objects are listed in the English royal treasury in 1664 as the property of the crown, having escaped the fate of much of the treasury that was sold at the time of the English Civil War.

A silver heraldic base for King John Casimir's crown, Abraham I Drentwett and Heinrich Mannlich, Augsburg, c. 1666

Besides Paris, Nuremberg was one of the primary cities for goldsmiths' work from the beginning of the sixteenth century until about 1648. Because of its strict guild rules and excellent artisans, Nuremberg was the main center of silversmithing in Germany at the time, attracting an international clientele. The type of covered cup was a regular feature of Nuremberg production during the second half of the seventeenth century and numerous examples by various silversmiths survive. The style rapidly spread throughout Germany and became known elsewhere. In northern Germany, cups like this were presented as gifts on special occasions, including accessions and coronations. They were also often filled with gold coins as a mark of respect to the recipient. One of the most famous silversmiths in Nuremberg during the late sixteenth and early seventeenth century was Hans Petzolt.

Another renowned center for the production of silver and gold objects during the seventeenth century was Augsburg. Like Nuremberg, Augsburg was celebrated because of dynasties of goldsmiths like the Drentwetts and the Billers, who were patronized by European rulers such as Leopold I, emperor of the Holy Roman Empire and John II Casimir of Poland. From about 1640 also Amsterdam was an active center for the production of silver decorated with lush floral motifs.

Silver relic coffin of St. Wojciech, Piotr von der Rennen, 1662, Gniezno Cathedral

In Poland the craft of silversmiths followed the general development of Western European traditions and styles. Most of the masters arrived from the major cities of Western Europe such as Nuremberg, Augsburg and Amsterdam. The brought with them new shapes and objects. The main centers of silver manufacture in Poland during the 17th and 18th centuries were the cities of Gdańsk and Wrocław. Chased goblets by Jakob Schmidt I and Lukas Kadau date from the 1620’s to 1640’s. The works by Christian Paulsen and Andrzej Mackenzen date from the middle of the 17th century. Works by different branches of the Rode family of jewelers, who were well known in Gdańsk from the mid-15th century, are also interesting, particularly Peter II Rode and his sons Peter III and Johann II. Larger silver castings represents relic coffins by Piotr von der Rennen in Gniezno and Wawel Cathedral. Spoons made by Polish masters in the 17th and 18th centuries were widely known. The spoons often have moralizing phrases engraved on their handles.

History

The symbol for the Moon has been used since ancient times to represent silver.

Cerro Rico, at Potosi, Bolivia, perhaps the world's most productive silver district, began mining during the Spanish Empire.

The word "silver" appears in Anglo-Saxon in various spellings such as seolfor and siolfor. A similar form is seen throughout the Teutonic languages (compare Old High German silabar and silbir). The symbol "Ag" is from the Latin for "silver", argentum (compare Greek αργυρος [argyros]), from the Indo-European root arg- meaning "white" or "shining".

Silver has been known since ancient times. It is mentioned in the book of Genesis, and slag heaps found in Asia Minor and on the islands of the Aegean Sea indicate that silver was being separated from lead as early as the 4th millennium BC.

In the Gospels, Jesus' disciple Judas Iscariot is infamous for having taken a bribe of silver from religious leaders in Jerusalem to turn Jesus Christ over to the Romans.

Set aside certain circumstances, Islam permits Muslim men to wear silver jewelry. The Prophet Muhammad (S.A.W.) himself wore a silver signet ring.

Price

Main articles: Silver as an investment and Silver standard

Silver is currently about 1/67th the price of gold by mass and approximately 57 times more valuable than copper. Silver once traded at 1/6th to 1/12th the price of gold, prior to the Age of Discovery and the discovery of great silver deposits in the Americas, including Peru, Mexico and the United States, such as the vast Comstock Lode in Virginia City, Nevada, USA. This then resulted in the debate over cheap Free Silver to benefit the agricultural sector, which was among the most prolonged and difficult in that country's history and dominated public discourse during the latter decades of the nineteenth century.

Over the last 100 years the price of silver and the gold/silver price ratio have fluctuated greatly due to competing industrial and store-of-value demands. In 1980 the silver price rose to an all-time high of US$49.45 per troy ounce. By December 2001 the price had dropped to US$4.15 per ounce, and in May 2006 it had risen back as high as US$15.21 per ounce. As of 2006, silver prices (and most other metal prices) have been rather volatile, for example, quickly dropping from the May high of US$15.21 per ounce to a June low of US$9.60 per ounce before rising back above US$12.00 per ounce by August. In March 2008 silver reached US$21.34 per ounce.

The price of silver is important in Judaic Law. The lowest fiscal amount that a Jewish court, or Beth Din, can convene to adjudicate a case over is a shova pruta (value of a Babylonian prutra coin). This is fixed at 1/8 of a gram of pure, unrefined silver, at market price.

Folklore and popular culture

Silver in European folklore has long been traditionally believed to be an antidote to various maladies and mythical monsters. Notably, silver was believed to be a repellent against vampires (this primarily originates from its holy connotations; also, mirrors were originally polished silver, and as such, vampires allegedly cannot be seen in them because they have no soul) and it was also believed that a werewolf, in his bestial form, could only be killed by a weapon or bullet made of silver. This has given rise to the term "silver bullet", which is used to describe things that very effectively deal with one specific problem.

In heraldry, the tincture argent, in addition to being shown as silver (this has been shown at times with real silver in official representations), can also be shown as white. Occasionally, the word "silver" is used rather than argent; sometimes this is done across-the-board, sometimes to avoid repetition of the word "argent" in blazon.

Precautions

Silver plays no known natural biological role in humans, and possible health effects of silver are a subject of dispute. Silver itself is not toxic but most silver salts are, and some may be carcinogenic.

Silver and compounds containing silver (like colloidal silver) can be absorbed into the circulatory system and become deposited in various body tissues leading to a condition called argyria which results in a blue-grayish pigmentation of the skin, eyes, and mucous membranes. Although this condition does not harm a person's health, it is disfiguring and usually permanent. Argyria is rare, and mild forms are sometimes mistaken for cyanosis.

See also

• Silver as an investment
• Silver coin
• Silver standard
• Silver mining
• Silver compounds
• Silver Nano

External links

• WebElements.com – Silver
• Silver Statistics and Information, USGS publications on the worldwide production of silver
• The Silver Institute A silver industry website
• A collection of silver items Samples of silver
• Transport, Fate and Effects of Silver in the Environment
• Picture in the Element collection from Heinrich Pniok