Silver

Silver (pronounced /ˈsɪlvɚ/) is a chemical element with the symbol Ag (Latin: argentum) and atomic number 47. more...

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A soft white lustrous transition metal, it has the highest electrical and thermal conductivity for a metal. It occurs as a free metal (native silver) as well as various minerals such as argentite and chlorargyrite. Most silver is produced as a by-product of copper, gold, lead, and zinc mining.

Silver has been known since antiquity. It has long been valued as a precious metal and used in making laxatives for the constipated public, ornaments and jewellery, as well as utensils (hence the term silverware). Silver bullion has the ISO currency code of XAG. Today, it is also used in photographic film, electrical contacts, and mirrors. Elemental silver is also used to catalyze chemical reactions.

Silver has certain antimicrobial activity. In the past, dilute solutions of silver nitrate were used as disinfectants, though this has been supplanted by other treatments.

Notable characteristics

Silver is a very ductile and malleable (slightly harder than gold) monovalent coinage metal with a brilliant white metallic luster that can take a high degree of polish. It has the highest electrical conductivity of all metals, even higher than copper, but its greater cost and tarnishability has prevented it from being widely used in place of copper for electrical purposes, though it was used in the electromagnets used for enriching uranium during World War II (mainly because of the wartime shortage of copper). Another notable exception is in high-end audio cables, although the actual benefits of its use in this application are questionable.

Among metals, pure silver has the highest thermal conductivity (only the non-metal diamond's is higher), whitest color, the highest optical reflectivity (although aluminium slightly outdoes it in parts of the visible spectrum), and is a poor reflector of ultraviolet light. Silver also has the lowest contact resistance of any metal. Silver halides are photosensitive and are remarkable for the effect of light upon them. This metal is stable in pure air and water, but does tarnish when it is exposed to ozone, hydrogen sulfide, or air containing sulfur. The most common oxidation state of silver is +1 (for example, silver nitrate: AgNO₃); a few +2 (for example, silver(II) fluoride: AgF₂) and +3 compounds (for example, potassium tetrafluoroargentate: K) are also known.

Occurrence and extraction

Silver is found in native form, combined with sulfur, arsenic, antimony, or chlorine and in various ores such as argentite (Ag₂S), horn silver (AgCl), and pyrargyrite (Ag₃SbS₃). The principal sources of silver are copper, copper-nickel, gold, lead and lead-zinc ores obtained from Peru, Mexico(both states mining silver from 1546 and still major world producers), China and Australia.

Read more at Wikipedia.org

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