INORGANIC CHEMISTRY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site silver (Ag) Native silver. Credit: USGS / US House of Representatives A lustrous, white, ductile, malleable, metallic element, occurring both uncombined and in ores such as galena and argentite. Silver is a noble metal and a transition element, occurring in group IB of the periodic table. It has the highest thermal and electrical conductivity of any metal. Silver is highly valued for jewelry, tableware, and other ornamental uses, and is widely used in coinage, photography, dental amalgam and soldering alloys,and electrical circuits. It is concentrated by various processes including cupellation and extraction with cyanide, and is refined by electrolysis. atomic number 47 relative atomic mass 107.87 electron configuration 1s22s22p63p23p63d104s24p6 5s14d10 atomic radius 144 pm relative density 10.50 melting point 960.8°C (1,761°F) boiling point 2,212°C (4,014°F) History Silver sometimes occurs in native form (found as an element in its natural state) and so was one of the first metals to humans. For thousands of years it has been valued for its beauty, and silver ornaments and jewelry dating from 4,000 BC have been found in Egyptian tombs. By about 800 BC it was in use as currency over the whole of the Middle East; silver coins were being minted in Greece about 700 BC. Although silver occurs free in nature, it is much more often found as silver sulfide, mixed with lead sulfide, in the ore galena. As early as 2,500 BC galena was mined and smelted; the silver was separated from the lead by cupellation. In this process the lead is oxidized in a furnace and removed as a scum from the surface of the molten silver which remains behind. The galena which was mined in Greece about 600 BC probably contained about 60 ounces of silver per ton of ore. Silver was mined in Europe, mainly in Bavaria and Spain, in medieval times. The discovery of the New World, and particularly Mexico and Peru, led to an enormous increase in the world supply of silver during the 16th and 17th centuries. Physical properties Silver is harder than gold but softer than copper. Apart from gold, it is the most malleable (bendable) and ductile (it can be stretchable) of all metals. One gram of silver can be drawn out into a thin wire 1½ km long, and it can be beaten out into sheets only 0.00025 mm thick. It is an excellent conductor of heat – better even than copper – and is also a slightly better conductor of electricity than copper. Chemical properties Silver, with few exceptions, is monovalent in its compounds. It is very resistant to attack by oxygen and tarnishes in air only if sulfur compounds are present, when a thin film of sulfide forms on its surface. It is quite resistant to attack by most acids, except nitric acid and concentrated sulfuric acid, and by most alkalis. Silver chloride, bromide, and iodide (see below) are all sensitive to light, and for this reason are used in the manufacture of photographic films and papers. It forms alloys, which are used in jewelry and coinage, with copper and gold. Compounds of silver Silver halides (AgX) are crystalline salts used in photography. The chloride is white, the bromide pale yellow, and the iodide yellow. On exposure to light, a crystal of of silver halide becomes activated, and is preferentially reduced to silver by a mild reducing agent (the developer). Silver nitrate (AgNO3) is a transparent crystalline solid, used as an antiseptic and astringent, especially for removing warts. Related category    • INORGANIC CHEMISTRY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP