Gold

Gold ischemical element inperiodic table that hassymbol Au (L. aurum)atomic number 79. A soft, shiny, yellow, heavy, malleable, ductile (trivalentunivalent) transition metal, gold does not reactmost chemicals butattacked by chlorine aqua regia. The metal occurs mainly uncombined as nuggetsrocksalluvial depositsis one ofcoinage metals. Goldused asmonetary standardmany nationsis also usedjewelry, dentistry,in electronics.

Tablecontents

1 Notable characteristics
2 Applications
3 History

3.1 Value

4 Occurrence
5 Compounds
6 Isotopes
7 Precautions
8 External links

Notable characteristics

Gold ismetallic element that exhibitsyellow color en mass but can be black, ruby, or purple when finely divided. Itarguablymost beautifulallelementsismost malleableductile metal known. In fact, 1 oz.gold can be hammered intosheet that covers 300 square feet. A soft metal, goldoften alloyedother metalsgivemore strength.

Goldalsogood conductorheatelectricityis not affected by airmost reagents. Itquite chemically unalterable by heat, moisture,most corrosive agentsthereforewell suitedits usecoinjewelry.

The colorsolid gold as well as ofintensely colored, often purple, colloidal solutions that can be made from itcaused byfact thatplasmon frequencythis element lies invisible range, which causes redyellow lightbe reflectedblue lightbe absorbed. Native gold contains usually eightten per cent silver, but often much more. Asamountsilver increases,color becomes whiter andspecific gravity lower.

Alloyscopper yieldredder metal, alloysirongreen, aluminum alloyspurple. Jewelry madecombinationscolored goldsold inwestern United States totourist trade as Black Hills gold.

Common oxidation statesgold include +1+3.

Applications

Pure goldtoo softordinary useis hardened by alloyingsilvercopper. Goldits many alloysmost often usedjewelry, coinageasstandardmonetary exchangemany countries. Becauseits superior electrical conductivityresistancecorrosionother desirable combinationsphysicalchemical properties, gold also emerged inlate 20th century as an essential industrial metal. Other uses;

Gold performs critical functionscomputers, communications equipment, spacecraft, jet aircraft engines, andhostother products.
The high electrical conductivityresistanceoxidationgold has ledits widespread use as thin layers electroplated onsurfaceelectrical connectorsensuregood, low-resistance connection.
Like silver, gold can formhard amalgam mercury,is sometimes useddental fillingss.
Colloidal gold (gold nanoparticles)an intensely colored solution thatcurrently studiedmany labsmedicalbiological applications. Italsoform used as gold paint on ceramics priorfiring.
Chlorauric acidusedphotographytoningsilver image.
Disodium aurothiomalate istreatmentrheumatoid arthritis (administered intramuscularly).
The gold isotope Au-198, (half-life: 2.7 days)usedsome cancer treatmentsfor treating other diseases.
Goldused ascoating enabling biological materialbe viewed underscanning electron microscope.
Goldoften symbolic forhighest or best achievement. Likeblue ribbon,gold medal ishighest award inOlympicsmany other competitions.

Sinceisgood reflectorboth infraredis inert light, itused forprotective coatings on many artificial satellites.

History

Gold (Sanskrit Jval; Anglo-Saxon gold; Latin aurum all meaning "gold") has been knownhighly valued since ancient times. Egyptian hieroglyphs from 2600 BC describemetalgoldmentioned several times inOld Testament.

Gold hasbeen considered one ofmost precious metals,its value has been used asstandardmany currencies (known asgold standard)history. Gold has been used assymbolpurity, value, royalty,particularly roles that combine these properties (see gold album).

The primary goal ofalchemists wasproduce gold from other substances, such as lead - Thoughwere never successful at this attempt,alchemists promoted an interestwhat can be donesubstances,this laidfoundationtoday's chemistry. Many competitions awardgold medal towinner, silver tosecond-place finisher,bronze tothird. The largest gold depository inworld isU.S. Federal Reserve Bank.

Value

Like other precious metals, goldmeasured by troy weightwhen italloyedother metalsterm caratusedindicateamountgold present24 carats being pure gold.

Historical gold was usedback currency insystem known asgold standardwhich one unitcurrency was equivalent tocertain amountgold.

Forverytimevaluegold was set byUnited States at $20.67 per troy ounce but1934valuegold was fixed at $35.00 per troy ounce. Because ofgold crisis, on March 17, 1968,two-tiered pricing scheme was established whereby gold was still usedsettle international accounts atold $35.00 per troy ounce butpricegold onprivate market was allowedfluctuate, this two-tiered pricing system was abandoned1975 whenpricegold was allowedfluctuate. Since 1968pricegold onopen market has widely fluctuated reaching $620/troy oz.January 1980 but later dropped$410/troy oz by January 1990.

Becauseits use asreserve storevalue,possessiongoldsometimes restricted or banned. WithinUnited States,private possessiongold except as jewelrycoin collecting was banned between 19331975.

Astangible investment goldoften held as part ofportfolio because overlong term gold has an extensive historymaintaining its value. However, gold becomes particularly desirabletimesextremely weak confidenceduring hyperinflation because gold maintains its value even as fiat money becomes worthless.

Futures contracts based on gold currently trade onCOMEX (Commodity Exchange) which issubsidiary ofNew York Mercantile Exchange. Speculation aboutfuture pricegoldcarried on here.

Occurrence

Dueits relative chemical inertness, gold oftenfound asnative metal, occasionally as large nuggets, but usually as minute flakessome minerals, quartz veins, slate, metamorphic rocksin alluvial deposits that originated from these sources. Goldwidely distributed,very often associated withminerals quartz or pyriteis combinedtellurium inminerals petzite, calaveritesylvanite. Goldextracted from alluvium by techniquesplacer mining. South Africa issourceabout two-thirds ofworld's gold supply (minesSouth Dakota Nevada supply two-thirdsgold used inUnited States).

Goldextracted from ores throughusecyanide, amalgam,smelting. Refining ofmetalfrequently accomplished by electrolysis. This metal occurssea water at 0.12 mg/ton depending on sample location. However, thereno profitable methodrecovering gold from sea water yet.

Although goldimportantindustry andarts,also retainsunique status among all commodities aslong-term storevalue. It has been estimated that allgold inworld that has ever been refined could formsingle cube 20 m (60 ft) onside.

Compounds

Auric chloride (AuCl₃)chlorauric acid (HAuClAuCl₄) aremost common compoundsgold. Although gold isnoble metalcan form many compounds

It dissolvesAqua regiaformAuCl₄^- ion
Gold halides (F,Cl,Br,I)
Gold chalcogenides (O, S, Se,Te)
Gold cluster compounds

Isotopes

Thereonly one stable isotopegold,18 radioisotopes Au-195 beingmost stable withhalf-life186 days.

Precautions

The human body does not absorb this metal wellcompoundsgoldnot normally very toxic. Liver kidney damage has, however, been reportedup50%arthritis patients treatedgold-containing drugs.

External links

Goldalsocolor,shadeyellow.

Inmusic industry, Gold iscertification forcertain numberunits shipped. InUS, itawarded byRIAA (see RIAA certification)stands500,000 records sold.