Gold

{| border="1" cellpadding="2" cellspacing="0" align="right" style="margin-left: 0.5em;" | colspan="2" cellspacing="0" cellpadding="2" | {| align="center" border="0" | colspan="2" align="center" | platinum – gold – mercury (element) |- | rowspan="3" valign="center" | Silver
Au
Roentgenium

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Periodic table (standard)

|} |- ! colspan="2" align=center bgcolor="#ffc0c0" | General |- | List of elements by name, List of elements by symbol, List of elements by number | Gold, Au, 79 |- | Chemical series | transition metals |- | periodic table group, periodic table period, periodic table block | group 11 element, period 6 element, d-block |- | Density, Mohs hardness scale | 19300 kilogram per cubic metre, 2.5 |- | color | align="center" | Metallic yellow
|- ! colspan="2" align="center" bgcolor="#ffc0c0" | Atomic properties |- | Atomic weight | 196.96655 unified atomic mass unit |- | Atomic radius (calc.) | 135 (174) picometre |- | Covalent radius | 144 pm |- | van der Waals radius | 166 pm |- | Electron configuration | [xenon] 4f-orbital¹⁴ 5d¹⁰ 6s-orbital¹ |- | electron 's per energy level | 2, 8, 18, 32, 18, 1 |- | Oxidation states (Oxide) | 3, 1 (amphoteric) |- | Crystal structure | Cubic face centered |- ! colspan="2" align="center" bgcolor="#ffc0c0" | Physical properties |- | State of matter | Solid |- | Melting point | 1337.33 Kelvin (1947.52 �Fahrenheit) |- | Boiling point | 3129 K (5173 �F) |- | Molar volume | 10.21 cubic metre per mole |- | Heat of vaporization | 334.4 kilojoule per mole |- | Heat of fusion | 12.55 kJ/mol |- | Vapor pressure | 237 Pascal at 1337 K |- | Speed of sound | 1740 metre per second at 20 �C |- ! colspan="2" align="center" bgcolor="#ffc0c0" | Miscellaneous |- | Electronegativity | 2.54 (Pauling scale) |- | Specific heat capacity | 128 joule per kilogram-kelvin |- | Electrical conductivity | 45.2 siemens (unit)/m |- | Thermal conductivity | 317 watt per metre-kelvin |- | 1^st ionization potential | 890.1 kJ/mol |- | 2^nd ionization potential | 1980 kJ/mol |- ! colspan="2" align="center" bgcolor="#ffc0c0" | Most stable isotopes |- | colspan="2" | {| border="1" cellspacing="0" cellpadding="2" width="100%" |Isotope |natural abundance |half-life |decay mode |decay energy fJ |decay product |- | ¹⁹⁵Au | synthetic radioisotope | 186.10 d | electron capture | 0.227 | Platinum |- | ¹⁹⁶Au | synthetic radioisotope | 6.183 d | electron capture
beta emission^- | 1.506
0.686 | Platinum
Mercury (element) |- | ¹⁹⁷Au || 100 % | colspan="4" | Au is stable isotope with 118 neutrons |- | ¹⁹⁸Au | synthetic radioisotope | 2.69517 d | beta emission^- | 1.372 | Mercury (element) |- | ¹⁹⁹Au | synthetic radioisotope | 3.169 d | beta emission^- | 0.453 | Mercury (element) |} |- ! colspan="2" align="center" bgcolor="#ffc0c0" | SI units & standard temperature and pressure are used except where noted. |} Gold is a chemical element in the periodic table that has the symbol Au (Latin ''aurum'') and atomic number 79. A soft, shiny, yellow, heavy, malleable, ductile (trivalent and univalent) transition metal, gold does not react with most chemicals but is attacked by chlorine, fluorine and aqua regia. The metal occurs as gold nugget or grains in rocks and in alluvial deposits and is one of the coinage metals. Gold is used as a Gold standard for many nations and is also used in jewelry, dentistry, and in electronics. Its ISO 4217 is XAU. == Notable characteristics == Gold is a metallic element with a characteristic yellow color, but can also be black or ruby when finely divided, while colloidal solutions are intensely colored and often purple. These colors are the result of gold's plasmon frequency lying in the visible range, which causes red and yellow light to be reflected and blue light to be absorbed. It is one of only three metals which have an actual easily-identifiable color; the other two are copper, which is red, and caesium, which has a gold color. It is the most malleable and ductility metal known; a single gram can be beaten into a sheet of one square meter, or an ounce into 300 square foot. A soft metal, gold will readily form alloys with many other metals. This can be done to increase its strength, or create several exotic colors, sold for instance in the western United States to the tourist trade as "Black Hills" gold. Adding copper yields a redder metal, iron green, aluminium purple, platinum metals white, and natural bismuth together with silver alloys produce black. Native gold contains usually eight to ten per cent silver, but often much more — alloys with a silver content over 20% are called electrum. As the amount of silver increases, the color becomes whiter and the Relative density lower. Gold is a good conductor of heat and electricity, and is not affected by air and most reagents. Heat, moisture, oxygen, and most corrosion agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; conversely, halogens will chemically alter gold, and aqua regia dissolves it. Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduction (chemistry) and Precipitation (chemistry) out as gold metal by the addition of virtually any other metal as the reducing agent. The added metal is oxidation and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate. == Applications== Pure gold is too soft for ordinary use and is hardened by alloying with silver, copper, and other metals. Gold and its many alloys are most often used in jewelry, Coin and as a standard for money exchange in many countries. Because of its superior electrical conductivity and resistance to corrosion and other desirable combinations of physical and chemical properties, gold also emerged in the late 20th century as an essential industrial metal. Other uses: *Gold can be made into thread and used in embroidery. *Gold performs critical functions in computers, communications equipment, spacecraft, jet aircraft engines, and a host of other products. *The high electrical conductivity and resistance to oxidation of gold has led to its widespread use as thin layers Electroplating on the surface of electrical connectors to ensure a good, low-resistance connection. *Gold is used in restorative dentistry especially in tooth restorations such as crown (dentistry) and bridges. *Colloidal gold (a gold nanoparticle) is an intensely colored solution that is currently studied in many labs for medical, biological and other applications. It is also the form used as gold paint on ceramics prior to firing. *Chlorauric acid is used in photography for toning the silver image. *Gold(III) chloride is used as a catalyst in organic chemistry. It is also the usual starting point for making other gold Inorganic compound. *Disodium aurothiomalate is a treatment for rheumatoid arthritis (administered intramuscularly). *The gold isotope Au-198, (half-life: 2.7 days) is used in some cancer treatments and for treating other diseases. * Gold is used as a coating enabling biological material to be viewed under a scanning electron microscope. * Many competitions and honors, such as the Olympics and the Nobel Prize, award a gold medal to the winner (with silver to the second-place finisher, and bronze to the third.) *Since it is a good reflector of both infrared and visible light, it is used for the protective coatings on many artificial satellites. *Gold flake is used on and in some gourmet sweets and drinks. Having no reactivity it adds no taste but is taken as a delicacy. *White gold (an alloy of gold with platinum, palladium, nickel, and/or zinc) serves as a substitute for platinum. *Green gold (a gold/silver alloy) is used in specialized jewelry while gold alloys with copper (reddish color) are more widely used for that purpose. == History == Gold (Sanskrit ''jval'', Greek language χρυσος [''khrusos''], Latin ''aurum'' for "shining dawn", Anglo-Saxon language ''gold'', Chinese 金 [''jīn'']) has been known and highly valued since prehistoric times. It may have been the first metal used by humans and was valued for ornamentation and rituals. Egyptian hieroglyphs from as early as 2600 BC describe gold, whose king Tushratta of the Mitanni claimed was as "common as dust" in Egypt. Egypt and Nubia had the resources to make them major gold-producing areas for much of history. Gold is also mentioned several times in the Old Testament. The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia between 630s BC. The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion by Native American peoples, especially in Central America, Peru, and Colombia. Gold has long been considered one of the most precious metals, and its value has been used as the standard for many currency (known as the gold standard) in history. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties (see gold album). Gold in antiquity was relatively easy to obtain geologically however 75% of all gold ever produced has been extracted since 1910.[http://www.goldsheetlinks.com/production2.htm] It has been estimated that all the gold in the world that has ever been refined would form a single cube 1 E2 m (66 ft) a side. The primary goal of the alchemy was to produce gold from other substances, such as lead — presumably by the interaction with a mythical substance called the philosopher's stone. Although they never succeeded in this attempt, the alchemists promoted an interest in what can be done with substances, and this laid a foundation for today's chemistry. Their symbol for gold was the circle with a point at its centre (☉), which was also the astrology symbol, the Egyptian Egyptian hieroglyph and the ancient Chinese character for the Sun (now 日). For modern attempts to produce artificial gold, see gold synthesis. During the 19th century gold rushes occurred whenever large gold deposits were discovered, including the California gold rush, Colorado gold rush, Central Otago goldrush, Australia, Witwatersrand, Black Hills, and Klondike gold rushes. Because of its historically high value, much of the gold mined throughout history is still in circulation in one form or another. == Value == Sveriges_Riksbank,_form_the_base_of_many_monetary_systems.">image:Gold ingots.jpg|thumb|200px|right|Gold ingots like these, from the Sveriges Riksbank, form the base of many monetary systems. Like other precious metals, gold is measured by troy weight and by grams. When it is alloyed with other metals the term ''carat (purity)'' or ''karat'' is used to indicate the amount of gold present, with 24 carats being pure gold and lower ratings proportionally less. The purity of a gold bar can also be expressed as a decimal figure ranging from 0 to 1, known as the millesimal fineness, such as 0.995. The price of gold is determined on the open market, but a procedure known as the Gold Fixing in London, originating in 1919, provides a twice-daily benchmark figure to the industry. Historically gold was used to back currency in an economic system known as the gold standard in which one unit of currency was equivalent to a certain weight of gold. As part of this system, governments and central banks attempted to control the price of gold by setting values at which they would exchange it for currency. For a long period the United States government set the price of gold at $20.67 per troy weight ($664.56/kg) but in 1934 the price of gold was set at $35.00 per troy ounce ($1125.27/kg). By 1961 it was becoming hard to maintain this price, and a pool of US and European banks began to act together to defend the price against market forces. On March 17 1968, economic circumstances caused the collapse of the gold pool, and a two-tiered pricing scheme was established whereby gold was still used to settle international accounts at the old $35.00 per troy ounce ($1.13/g) but the price of gold on the private market was allowed to fluctuate; this two-tiered pricing system was abandoned in 1975 when the price of gold was left to find its free-market level. Central banks still hold historical official gold reserves as a reserves asset although the level has generally been declining. The largest gold depository in the world is the U.S. Federal Reserve Bank. Since 1968 the price of gold on the open market has ranged widely, with a record high of $850/oz ($27,300/kg) on 21 January 1980, to a low of $252.90/oz ($8,131/kg) on 21 June 1999 (London Fixing). Prices have risen to the $420/oz ($13,500/kg) mark in 2004, due to a depreciation of the US dollar (an inverse relation between the prices exists to a certain extent). The price of gold has remained relatively constant in currencies not tied to the US dollar; for example, it has not varied by more than 10% from Euro330/oz (€10,600/kg) or Australian dollar560/oz (A$18,000/kg) during this time. Because of its use as a reserve store of value, the possession of gold is sometimes restricted or banned. Within the United States, the private possession of gold except as jewelry and coin collecting was banned between 1933 and 1975. President Franklin D. Roosevelt confiscated gold by [http://www.the-privateer.com/1933-gold-confiscation.html Executive Order 6102], and President Richard Nixon closed the gold window by which foreign countries could exchange American dollars for gold at a fixed rate. In the first few years of the 21st century, reports started to circulate that Malaysia was planning a return to the gold standard -- to issue and use gold dinars as currency in international trade. The purported purpose of this move would be to reduce dependence on the United States dollar as a reserve currency, and to establish a non-debt-backed currency in accord with Islamic law against the charging of interest. [http://www.islamidag.dk/ulamaongold.html] Nonetheless, gold dinar currency has not yet emerged. [http://english.aljazeera.net/NR/exeres/E7515CEE-880E-492F-B225-A94E21D90D2B.htm] [http://www.mineweb.net/columns/american_notes/336075.htm] As a tangible investment gold is sometimes held as part of a portfolio because over the long term gold has an extensive history of maintaining its value. It has in the last century gained ground in relation to fiat currencies owing to inflation. Speculating in gold, attempting to buy low and sell high, carries large transaction costs. However, gold does become particularly desirable in times of extremely weak confidence and during hyperinflation because gold maintains its value even as fiat money becomes worthless. People who, despite the risks, enjoy investing in gold are known as goldbugs. Futures contracts based on gold currently trade on various exchanges around the world. In the US this occurs primarily on COMEX (Commodity Exchange) which is a subsidiary of the New York Mercantile Exchange. Speculation about the future price of gold and other commodities is carried on at COMEX. == Occurrence == octahedron_formations">Image:Native gold nuggets.jpg|175px|right|thumb|Native gold from California (top) and Australia (bottom), showing octahedron formations Due to its relative chemical inertness gold is usually found as the native metal or alloy. Occasionally large accumulations of native gold (also known as gold nugget) occur but usually gold occurs as minute grains. These grains occur between mineral grain boundries or as inclusions within minerals. Common gold associations are quartz often as veins and sulfide minerals. The most common sulfide associations are pyrite, chalcopyrite, galena, sphalerite, arsenopyrite, stibnite and pyrrhotite. Rarer mineral associations are petzite, calaverite, sylvanite, muthmannite, nagyagite and krennerite. Gold is widely distributed in the earth's crust at a background level of 0.03 gram/1000 kg (0.03 Parts per million). Hydrothermal ore deposits of gold occur in metamorphic rocks and igneous rocks; alluvial deposits and placer deposits originate from these sources. The primary source of gold is usually igneous rocks or surface concentrations. A deposit usually needs some form of secondary enrichment to form an economically viable ore deposit: either chemical or physical processes like erosion or solution or more generally metamorphism, which concentrates the gold in sulfide minerals or quartz. There are several primary deposit types, common ones are termed reef or vein. Primary deposits can be weathered and eroded, with most of the gold being transported into stream beds where it congregates with other heavy minerals to form placer deposits. In all these deposits the gold is in its native form. Another important ore type is in sedimentary black shale and limestone deposits containing finely disseminated gold and other platinum group metals. Gold occurs in sea water at 0.1 to 2 milligram/1000 kg (0.1 - 2 Parts per billion) depending on sample location. == Gold Production == Economic gold extraction can be achieved from ore grades as little as 0.5 g/1000 kg (0.5 ppm) on average in large easily mined deposits, typical ore grades in open-pit_mining mines are 1 - 5 g/1000 kg (1-5 ppm), ore grades in underground or hard_rock_mining mines are usually at least 3 g/1000 kg (3 ppm) on average. Ore grades of 30 g/1000 kg (30 ppm) are usually needed before gold will be visible to the naked eye, therefore even in gold mines you will often not see any gold. gold extraction from alluvium ores by techniques of placer mining and from hard rock ores using extractive metallurgy. Refining of the metal is frequently accomplished by chlorination or electrolysis. Gold occurs in sea water at 0.1 to 2 milligram/1000 kg (0.1 - 2 Parts per billion) depending on sample location. However, as of 2004 there is no profitable method for recovering gold from sea water. Since the 1880s South Africa has been the source for about two-thirds of the world's gold supply. The city of Johannesburg was built atop the world's greatest gold finds. Gold fields in the Orange Free State and the Transvaal were deep and require the world's deepest mines. The Boer War of 1899–1901 between the United Kingdom and the white Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa. Other major producers are Canada, United States and Western Australia. Mines in South Dakota and Nevada supply two-thirds of gold used in the United States. == Compounds/isotopes == Auric chloride (Auchlorine₃) and chlorauric acid (hydrogenAuCl₄) are the most common compounds of gold. Gold compounds can be aurous (univalent, +1) or auric (trivalent, +3). Gold also can under extreme conditions form a +5 state with fluorine (gold pentafluoride, AuF₅), as well as (unusually for a metal), a -1 state. Such compounds containing the Au^- anion are called ''aurides'' and include caesium auride, CsAu, rubidiumAu, and tetramethylammonium auride, (CH₃)₄N⁺ Au^-. Although gold is a noble metal it can form many compounds (auric chloride and chloroauric acid are the most common). It also forms: * It dissolves in Aqua regia to form the AuCl₄^- ion *Gold halides (fluorine,chlorine,bromine,iodine) *Gold chalcogenides (oxygen, sulfur, selenium,tellurium) *Gold cluster compounds *Aurous hydrazine: an explosive olive-green powder, AuN₂H₄, known archaically as ''aurum fulminans'' There is only one stable isotope of gold, and 18 radioisotopes with Au-195 being the most stable with a half-life of 186 days. == Precautions == The human body does not absorb gold very well, thus compounds of gold are not normally very toxic. Liver and kidney damage has, however, been reported for up to 50% of arthritis patients treated with gold-containing drugs. Gold used in dentistry is widely regarded as the safest form of restorative material, as well as the most successful. == References == *[http://periodic.lanl.gov/elements/79.html Los Alamos National Laboratory – Gold] *[http://www.infoplease.com/ce6/sci/A0821152.html The Columbia Electronic Encyclopedia, 6th ed] == External links == *[http://www.webelements.com/webelements/elements/text/Au/index.html WebElements.com – Gold] (also used as a reference) *[http://environmentalchemistry.com/yogi/periodic/Au.html EnvironmentalChemistry.com – Gold] (also used as a reference) *[http://mineral.galleries.com/minerals/elements/gold/gold.htm Mineral Galleries - Native Gold] *[http://www.kitco.com Gold prices and economy] *[http://www.galmarley.com Facts, figures and arguments for gold bugs!] *[http://www.bullionvault.com Retail gold exchange] *[http://www.1849.org/ Gold, Greed & Genocide] *[http://www.lateralscience.co.uk/gold/auriferous.html ''Getting Gold'' 1898 book] Gold Chemical elements Transition metals la:Aurum ms:Emas simple:Gold vi:V�ng

Gold

== New format == Article changed over to new WikiProject Elements format by user:maveric149 == Information Sources == Some of the text in this entry was rewritten from [http://periodic.lanl.gov/elements/79.html Los Alamos National Laboratory - Gold]. Additional text was taken directly from [http://minerals.usgs.gov/minerals/pubs/commodity/gold/ USGS Gold Statistics and Information], from the Elements database 20001107 (via [http://www.dict.org dict.org]), Webster's Revised Unabridged Dictionary (1913) (via [http://www.dict.org dict.org]) and WordNet (r) 1.7 (via [http://www.dict.org dict.org]). Data for the table were obtained from the sources listed on the subject page and WikiProject Elements but were reformatted and converted into SI units. == NPOV == Why's the neutrality of this article being disputed? -- User:Schneelocke 12:48 24 Jun 2003 (UTC) I wonder that, too. The dispute was flagged by User:Eszett, but it's not at all obvious to me why. The flag doesn't seem to add any value to the page. User:Andrewa 10:28 3 Jul 2003 (UTC) :Removed idiodic and insulting dispute notice. --User:Maveric149 15:59 3 Jul 2003 (UTC) ::Sounds good to me. Whatever the supposed dispute, it should be described in the talk page. This is especially important in an article as long, and with such a variety of information, as this one, but IMO it should be a matter of course anyway. It makes it difficult, but I agree there's no obvious basis for an NPOV dispute. Great article. User:Andrewa 17:57 3 Jul 2003 (UTC) :::Thanks for the support and compliment. :) --User:Maveric149 ::::In any event, the edit which added the NPOV notice had a blank summary. Kinda leaves you guessing... --User:Trainspotter == Modern cultural aspects of gold == Hmmmm... I see the new section heading and note I added have both been deleted mere minutes later, and the cultural stuff I had started to put up is now in "history". Interesting approach, and well written. But the material I want to add is about cultural aspects of Gold now, rather than its history. I'll leave this project a while and think about it. Or would someone else like to have a go? User:Andrewa 23:53, 30 Aug 2003 (UTC) == Alloys used in jewellery == It will be interesting if somebody can provide information about the most typical alloys used in jewelry User:Cuye == Peak price == The high price of gold was $850 per ounce which occurred in 1980, not $620, correct? == Perodic table listing missing == The right hand bar is missing the perodic table listing at the top like the other elements (i.e. radium). User:ShaunMacPherson == What was prohibited in the US between 1933 and 1975? == :"Within the United States, the private possession of gold except as jewelry and coin collecting was banned between 1933 and 1975." Surely other uses must have been permitted too - it has significant industrial uses, and was certainly used in computer circuitry during this period. Does anyone have a reference to what exactly was prohibited? User:Securiger 01:43, 26 May 2004 (UTC) ::Reference added--User:1pezguy 07:20, Jul 17, 2004 (UTC) == NPOV of hedge value of gold == "However, gold becomes particularly desirable in times of extremely weak confidence and during hyperinflation because gold maintains its value even as fiat money becomes worthless." NPOV? You have to be extremely carefull, because many gold investors constantly make statements and doom and gloom websites purporting to show the stable value of gold throughout economic crisis. == Colours of reflected light == "... caused by the fact that the plasmon frequency of this element lies in the visible range, which causes red and yellow light to be reflected and blue light to be absorbed." Unless my physics is mistaken, shouldn't it reflect red and _green_ light? ---- ==Value of gold== I wonder, why is gold considered to be valuable? I know it looks great but is that why? I am not asking because I don't think it should be considered as such, I'm just curioous. User:Jaberwocky6669 21:00, Aug 4, 2004 (UTC) :It is rare and does not degrade. --User:Maveric149 07:00, 5 Aug 2004 (UTC) ---- Which industry does the london benchmark provide for, financial? gold?, maybe it should say something like .......benchmark figure to the ?finacial? and ?gold? industry and ?general public?. User:Tridy 15:47, 10 Oct 2004 (UTC) ==disputed== As I explained in ''Making Stargate a Reality'' in the Stargate Technical forum of Ascifi.com (Ignore that temperature; it's a calcuotypo!), gold's ductibility and malleability are exceeded by at least three other metals, at STP even. If you look around the periodic table, you should see that for yourself without going into my essay. Then it should read "It is one of the most malleable and ductile metals known." User:Tridy 03:10, 29 Oct 2004 (UTC) Where did you get the gold alloy information? I'm especially interested in that AuAl combo. User:Lysdexia 08:37, 19 Oct 2004 (UTC) http://www.ajm-magazine.com/features/0704/purple.php User:Tridy 03:10, 29 Oct 2004 (UTC) ==coating== Can you say how it works? for example doesn't it have some diamond atoms mixed? there's no such things as diamond atoms! Diamond is tetrahedral (3-D) carbon!! Also, it wasn't mentioned that gold based comounds have been used for cancer treatment as well. - Frances 10/6/05

Gold

Gold

Gold

Transition metals

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