|Group||11||Melting point||961.78 oC, 1763.2 oF, 1234.93 K|
|Period||5||Boiling point||2162 oC, 3924 oF, 2435 K|
|Block||d||Density (g cm-3)||10.5|
|Atomic number||47||Relative atomic mass||107.868|
|State at 20°C||Solid||Key isotopes||107Ag|
|Electron configuration||[Kr] 4d105s1||CAS number||7440-22-4|
|ChemSpider ID||22394||ChemSpider is a free chemical structure database|
Silver is used to make mirrors, as it is the best reflector of visible light known, although it does tarnish with time. It is also used in dental alloys, solder and brazing alloys, electrical contacts and batteries. Silver paints are used for making printed circuits.
Silver bromide and iodide were important in the history of photography, because of their sensitivity to light. Even with the rise of digital photography, silver salts are still important in producing high-quality images and protecting against illegal copying. Light-sensitive glass (such as photochromic lenses) works on similar principles. It darkens in bright sunlight and becomes transparent in low sunlight.
Silver has antibacterial properties and silver nanoparticles are used in clothing to prevent bacteria from digesting sweat and forming unpleasant odours. Silver threads are woven into the fingertips of gloves so that they can be used with touchscreen phones.
Specific heat capacity
(J kg-1 K-1)
|235||Young's modulus (GPa)||82.7|
|Shear modulus (GPa)||30.3||Bulk modulus (GPa)||103.6|
Slag heaps near ancient mine workings in Turkey and Greece prove that silver mining started around 3000 BC. The metal was refined by cupellation, a process invented by the Chaldeans, who lived in what is now southern Iraq. It consisted of heating the molten metal in a shallow cup over which blew a strong draft of air. This oxidised the other metals, such as lead and copper, leaving only silver unaffected.
The rise of Athens was made possible partly through the exploitation of local silver mines at Laurium. These operated from 600 BC and right through the Roman era. In Medieval times, German mines became the main source of silver in Europe.
Silver was also mined by the ancient civilizations of Central and South America there being rich deposits in Peru, Bolivia and Mexico.
|Listen to Silver Podcast|
Chemistry in Its Element - Silver
You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.
Hello! Welcome to Chemistry in its element. This week, we're demystifying the element behind the photograph and to cross your cognitive palm with Silver, here's Victoria Gill.
Its lustre shine has been coveted since ancient times. It's not just rare or precious, as its more expensive cousin, Gold, but there is evidence from as early as 3000 BC that humans extracted Silver from naturally occurring Silver sulphide deposits in rocks to make coins and jewellery. These coins actually form the basis for the economies of some ancient Mediterranean civilizations. It's a soft and pliable metal with a relatively low melting point and that means it can be hammered and moulded into shape, so the same metal that was used to make money that was gradually outdated could also be transformed into vases, platters, cutlery and goblets; tableware that has created displays of household wealth through the centuries. But a gleaming collection of Silverware isn't easy to maintain. The metal reacts with sulphur in the air, rapidly forming a dull, dark Silver sulphide tarnish that has to be polished off. So it's a high maintenance element; another reason why it has always been outshone by Gold. But the same chemical properties that tarnished its image let it to make another mark in history, by allowing history itself to be recorded in the photograph.
In 1727, a German physicist called Johann Heinrich Schulze found that a paste of chalk and Silver nitrate salt was blackened by light. He used stencils to produce black images with the paste. This reaction, the dawn of photography, was all thanks to the fact that Silver salts are sensitive to light. A photon of light hitting the negative nitrate anion frees an electron, which ultimately combines with the positive Silver ions to make neutral Silver metal, darkening the surface of the material. When in 1840, Henry Talbot discovered an additional chemical twist, that is so called latent Silver image, that had been briefly exposed onto a layer of Silver iodide could be revealed using Gallic acid, the effect was seen as magical, a devilish art. But this mystical development of an invisible picture was a simple reduction reaction; the Gallic acid helping to reduce photosensitized Silver ions into Silver metal. Hollywood could never have existed without the chemical reaction that gave celluloid film its ability to capture the stars and bring them to the aptly dubbed Silver screen.
Digital photography may now have eclipsed the Silver image, but the metal's ability to conduct has given it an important role in the digital age. Silver is used on circuit boards and in batteries, where the conduction speed is needed that Copper for example, can't quite deliver. Even its most outdated properties are making resurgence. With new antibiotics running thin, a few researchers are returning to Silver as a coating to keep the bugs at bay. Silver metal is toxic to nasty bacteria, but not to us and there is even a tiny amount of it in our bodies, but that's yet to give up the secret of why it's there. For me, rather superficially, it's always been Gold's subtler, prettier counterpart.
Victoria Gill uncovering the secrets of the element that gave us the Silver screen. Next time on Chemistry in its element, John Emsley introduces a chemical that's mostly fallen from favour, perhaps with good reason.
This trouble-making element has attacked the ozone layer, and its mere presence has caused entire reservoirs to be drained.
And you can hear John Emsley telling the story of the brown element, Bromine, on next week's Chemistry in its element. I'm Chris Smith, thank you for listening. See you next time.
Chemistry in its elementis brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our web site at chemistryworld dot org forward slash elements.
Mining and Sourcing data: British Geological Survey – natural environment research council.
Text: John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.