Chemical Elements.com - Gold (Au) Contains an "Introduction to Tungsten", among other things If you know of any other links for Gold, please let me know Bentor, Yinon. Chemical Element.com - Gold. < For more information about citing online sources, please visit the MLA's Website . This page was created by Yinon Bentor. Use of this web site is restricted by this site's license agreement . Copyright © 1996-2012 Yinon Bentor. All Rights Reserved. It's Elemental - The Element Gold It's Elemental Melting Point: 1337.33 K (1064.18°C or 1947.52°F) Boiling Point: 3129 K (2856°C or 5173°F) Density: 19.282 grams per cubic centimeter Phase at Room Temperature: Solid Element Classification: Metal Period Number: 6 Group Number: 11 Group Name: none What's in a name? From the Sanskrit word Jval and the Anglo-Saxon word gold. Gold's chemical symbol comes from the the latin word for gold, aurum. Say what?

Gold is pronounced as GOLD. History and Uses: An attractive and highly valued metal, gold has been known for at least 5500 years. Gold is sometimes found free in nature but it is usually found in conjunction with silver , quartz (SiO2), calcite (CaCO3), lead , tellurium , zinc or copper . There is roughly 1 milligram of gold dissolved in every ton of seawater, although extracting it currently costs more than the gold is worth. It has been estimated that all of the gold that has currently been refined could be placed in a cube measuring 20 meters on a side. Gold is the most malleable and ductile of all known metals. A single ounce of gold can be beaten into a sheet measuring roughly 5 meters on a side. Thin sheets of gold, known as gold leaf, are primarily used in arts and crafts for gilding. One sheet of gold leaf can be as thin as 0.000127 millimeters, or about 400 times thinner than a human hair. Pure gold is soft and is usually alloyed with other metals, such as silver, copper, platinum or palladium , to increase its strength.

Gold alloys are used to make jewelry, decorative items, dental fillings and coins. The amount of gold in an alloy is measured with a unit called a karat. One karat is equal to one part in twenty-four, so an 18 karat gold ring contains 18 parts pure gold and 6 parts alloy material. Gold is a good conductor of heat and electricity and does not tarnish when it is exposed to the air, so it can be used to make electrical connectors and printed circuit boards. Gold is also a good reflector of infrared radiation and can be used to help shield spacecraft and skyscrapers from the sun's heat. Gold coated mirrors can be used to make telescopes that are sensitive to infrared light. A radioactive isotope of gold, gold-198, is used for treating cancer. Gold sodium thiosulfate (AuNa3O6S4) is used as a treatment for arthritis. Chlorauric acid (HAuCl4) is used to preserve photographs by replacing the silver atoms present in an image.

Estimated Crustal Abundance: 4×10-3 milligrams per kilogram Estimated Oceanic Abundance: 4×10-6 milligrams per liter Number of Stable Isotopes: 1 ( View all isotope data ) Ionization Energy: 9.226 eV Gold - Element information, properties and uses | Periodic Table Chemistry in its element: gold (Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) Chris Smith Hello, in this week's episode of Chemistry in its element, we're taking a flight on Concorde, dropping by Buckingham Palace and finding out what could form a film just 230 atoms thick. Going for gold for us this week, here's the legendary science broadcaster and populariser Johnny Ball. Johnny Ball The element gold. Gold is element 79 and its symbol is Au. Though the name is Anglo Saxon, gold originated from the Latin Aurum, or shining dawn, and previously from the Greek. It's abundance in the earth's crust is 0.004 ppm.

100% of gold found naturally is isotope Au-197. 28 other isotopes can be produced artificially and are all radioactive. Gold along with silver and copper, form a column in the periodic table. They are found naturally and were the first three elements known to man. They were all used as primitive money well before the first gold coins which appeared in Egypt around 3400 BC. Most gold is ancient or comes from Central American Aztecs and South American Incas brought to Europe by the Spanish and Portuguese in the 16th century, and which has since been recycled over and over again. In 1830 world output was no more than 12 tonnes per annum. But around that time, new gold discoveries were being made. Finds were discovered in Siberia, California, New South Wales and Victoria, Australia, Transvaal, South Africa, the Klondike and Alaska, and they all produced gold rushes. World production was then around 150 tonnes per year. It is now around 2300 tones per annum.

Because it is found in it's natural state and does not naturally alloy with anything else and because it is the heaviest metal, by sifting rock in water, the gold always falls to the bottom and all less dense impurities are washed away. The largest nugget was the Welcome Stranger nugget found in Victoria, Australia in 1869. It weighed over 71 kg. This type of nugget occurs naturally, but is very, very rare. Pure gold is 24 karat. 18 karat is 75% and 12 karat is 50% pure gold. Gold is the most malleable of all metals and soft enough to be cut with a knife. Stone age peoples hammered gold into plates for ornamental purposes. Really quite large amounts were gathered together. Though King Tutankhamun was a minor Pharaoh and died aged 18, his coffin alone contained 112 kg of gold. Egyptians also made thin gold sheets, utensils, vast varieties of jewellery and even gold thread. King Tut when he was buried had over 150 gold ornaments on his body. Today 1 gram can be beaten into a square metre sheet just 230 atoms thick.

1 cubic centimetre would make a sheet of 18 square metres. Concord's windscreen had a layer of gold to screen pilots from UV light and today it is often used in sky scraper windows to cut down both heat and UV from sunlight. 1 gram can be drawn to make 165 metres of wire 20 um (microns) thick (1/200th of a millimeter) The gold colour in the Buckingham Palace fence is actually gold covered, as it lasts 30 years, whereas gold paint (which contains no gold at all) lasts in tip top condition, only about a year. Sea water contains around 3 parts in a billion of gold, but there's never been found an economic means of recovering it. The Germans tried very hard during the second World War but failed miserably. The largest modern hoard is the 30,000 tons in the US Federal Reserve Bank in New York, which belongs to 18 different nations. It is estimated that all the world's gold gathered together would only make a cube around 18 metres per side - about 6000 cubic metres. And that's gold.

Chris Smith So now you know why pirates used to bite gold coins to see if they were real. It wasn't just for the camera because it looked good, it was because the metal was soft enough to be marked by teeth. That was Johnny Ball telling the story of gold. Next time on Chemistry in its element Victoria Gill introduces the chemical that founded the science of photography and also helped to launch the careers of successions of Oscar winners. Victoria Gill in 1840, Henry Talbot discovered an additional chemical twist, that a 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. 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. Chris Smith And you can hear Victoria Gill crossing your cognitive palm and lining your intellectual pocket with silver on next week's Chemistry in its element. I'm Chris Smith, thank you for listening, see you next time. (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com .

There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements . (End promo) Gold»the essentials [WebElements Periodic Table] Element News Gold: the essentials Most metals are metallic grey or silvery white whereas gold is characteristically a metallic yellow colour, in other words gold-coloured. Caesium is also gold coloured. The gold colour seems related to relativistic effects of the outermost gold orbitals. Small amounts of other metals alloyed with gold change the colour as well as mechanical properties such as hardness. White gold for jewellery is formed by mixing palladium, silver, or nickel with gold, although the result is green gold with certain proportions of silver. White gold is commonly used for wedding rings in the USA. Addition of some copper gives "rose gold", a soft pink colour. Remarkably other colours such as purple (a gold:aluminium alloy), blue (a gold:indium alloy) and even black (a gold:cobalt alloy) may be formed. Gold is usually alloyed in jewellery to give it more strength, and the term carat describes the amount of gold present (24 carats is pure gold).

It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft. on a side. It is metallic, with a yellow colour when in a mass, but when finely divided it may be black, ruby, or purple. CAS Registry ID : 7440-57-5 It is the most malleable and ductile metal; 1 ounce (28 g) of gold can be beaten out to 300 square feet. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most reagents. Gold is readily available commercially and its price changes day by day and is one of the most widely tracked commercial prices. The most common gold compounds are auric chloride (AuCl3) and chlorauric acid (HAuCl4). A mixture of one part nitric acid with three of hydrochloric acid is called aqua regia (because it dissolved gold, the King of Metals). It is unaffected by air and most reagents. It is found free in nature and associated with quartz, pyrite and other minerals.

Two thirds of the world's supply comes from South Africa, and 2/3 of USA production is from South Dakota and Nevada. Gold is found in sea water, but no effective economic process has been designed (yet) to extract it from this source. Gold Assay It is critical from the public's perspective that there is confidence in the claimed purity of any particular item made from precious metals. This confidence is provided by an 'assay' (test and assess) of the precious metal content of that item. It is impossible to tell the precious metal content of any item simply by looking at it. Precious metals such as old, silver, and platinum are too soft to use alone for making jewellery, cutlery and other goods. Quite properly they must be alloyed with base metals (which happen to be cheap) for manufacturing. The assay protects the consumer by ensuring sure that not too much base metal was used. It also safeguards responsible manufacturers by providing an independent assessment of quality and content that in which the public has confidence. There has been an "Assay Office" at Sheffield in England since 1773 when local silversmiths won the right from Parliament to assay silver in Sheffield.

The 1773 Act of Parliament appointed 30 local men as 'Guardians of the Standard of Wrought Plate in the Town of Sheffield' to supervise the work of the Office. In 1773 Sheffield already had an established tradition of fine silverware production and the number of Guardians who were also silversmiths was restricted to just ten to ensure that the Assay Office offered an independent and impartial service. This safeguard was to ensure the Office was run for the benefit of the consumer as well as the manufacturer. Once a piece was assayed, it was marked using a "hallmark", making the hallmark perhaps the oldest mark of consumer protection. The first UK Assay Office was and is based at Goldsmiths' Hall in London. It founded around 1300, and is from where the term "hallmarking" originates, meaning "marked in Goldsmiths' Hall". While there are assay offices in the USA, there is no hallmarking scheme. Cartoon by Nick D Kim ( [Science and Ink] , used by permission). Gold: historical information Gold was discovered by known since ancient times in unknown at not known.

Origin of name : from the Anglo-Saxon word "gold" (the origin of the symbol Au is the Latin word "aurum" meaning "gold"). Gold has always fascinated people and gold is certainly one of the very first metals known. Nobody knows who picked up a gold nugget first but it would have been because it was shiny. Gold was highly valued from from the earliest recorded times in history. It seems that the Egyptians developed gold smelting some 5600 years ago (about 3600 BC) using clay blowpipes to heat the smelter contents. Egyption inscriptions dating back to 2600 BC describe gold. Gold workers from Mesopotamia (known now as Iraq) made one of the earliest known pieces of gold jewellery in about 2600 BC. Gold is mentioned several times in the Old Testament. Tutankhamun's funeral mask is one of the most iconic gold pieces known. It was made around 1223 BC and is a stunning piece of ancient gold craftsmanship.

The first use of gold in dentistry as the Etruscans (an ancient Italian civilisation from an area corresponding now to Tuscany) begin securing substitute teeth with gold wire, and with astonishing skill. This was as early as 700-600 BC. Apparently Etruscan craftsmen made gold dental bridges for women so that they could show display their wealth and status. Some women had their incisors removed so that they could be fitted with the gold prosthetics. The Etruscans probably learned dentistry from the Egyptians, Phoenicians, and Greeks but took the art much further. Many specimens of Etruscan dental fittings are to be found in Italian and other museums. Adapted from M. Don Clawson: Phoenician Dental Art and History of Dentistry Research Page, Newsletter, 8 May 2006 . The dental work illustrated above from the 7th century BC is a fine Etruscan specimen. Gold loops were fitted over the remaining natural teeth, set in place, and maintained by solder. The patient's missing teeth were replaced by either the teeth of human beings and on occasion the tooth of an ox.

Bio-compatibility, malleability and corrosion resistance make gold valuable even today in dental applications. Colloidal gold has been used since Roman times to colour glass shades of yellow, red, or violet. Melting gold powder into glass diffuses gold nanoparticles into the glass, these refract light, giving the glass a luminous red glow. THe precise colour depends upon the form of the colloidal gold. Faraday (1857) recognised that the colour is due to the minute size of the gold particles and called the sample he made 'activated gold'. In 1898 Richard Adolf Zsigmondy prepared the first colloidal gold in dilute solution. Today, colloidal gold is made by the addition of reducing agents to dilute solutions of Au(III) (the auric ion). One famous form is that made by the use of tin dichloride (SnCl2) as reducing agent. This is a very stable form of colloidal gold and is known as the "Purple of Cassius". It is suitable for colouring ceramics and glasses, and in addition is a good test for Au(III). The form that Faraday studied was made using phosphorus to reduce gold chloride.

Colloidal gold has been used since Ancient Roman times to colour glass intense shades of yellow, red, or mauve, depending on the concentration of gold, Gold is one of the elements which has an alchemical symbol, shown below (alchemy is an ancient pursuit concerned with, for instance, the transformation of other metals into gold). Hallmarking practice established The world's first "hallmarking" system was established at Goldsmith's Hall in London in 1300 AD. London's Assay Office is still there. THe purpose of the hallmarking system is to determine and guarantee the quality of precious metals such as gold. Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms.

Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for gold is shown below. [See History of Chemistry, Sir Edward Thorpe, volume 1, Watts & Co, London, 1914.] Gold has been the basis of many currencies over the centuries and so for economic reasons, among others, the possession of gold was or is restricted in some countries. Notably, private ownership of gold (apart from as jewellery and coins) was banned between 1933 and 1975. In 1422 the Venice Mint made ("struck") 1.2 million gold ducats using 4.26 metric tonnes of gold. These small coins (each about 3.5 g) were popular perhaps because they were easy to make and are highly transportable. In 1717 Great Britain moved to a pure gold standard.

The British government linked the currency to gold at a fixed rate (77 shillings, ten and a half pennies per ounce of gold). Image: Classical Numismatic Group, Inc. The Californian Gold Rush of 1848+1855 started on 24 January 1848 when gold was found by James W. Marshall at Sutter's Mill, in Coloma, California. Although attempts were made to keep the discovery quiet, news leaked out and the result was the migration of 300,000 people to California from the United States and beyond. The New York Herald was the first East Coast newspaper to report the discovery of gold and on 5 December 1848, President James Polk confirmed the discovery in an address to Congress. The gold-seekers were called the "Forty-niners" and often had a very hard time. Prospectors retrieved the gold from streams and riverbeds using low-technology methods such as panning. More sophisticated methods of gold recovery were eventually developed. Gold worth tens of billions of US dollars (2010 equivalent price) was extracted. Some became wealthy but many finished with little profit and a lot of heartache.

Today, the forty-niners name lives on in the name of the San Francisco 49ers, an American football team in California. Some years later in 1885 the South African Gold Rush began. An Australian miner, George Harrison, found gold on Langlaagte farm near Johannesburg while digging to build a house. South Africa became the source of almost one-half of the world's gold. Gold around us Read more » Gold is not a necessary trace element for living things and neither are any of the other third row d-block elements. In part this may be because there is little gold in the biosphere with which living things might experiment and also because there are few ways for living things to convert gold into a suitable soluble form. There do seem to be a few plants that accumulate gold, perhaps because they are associated with microorganisms containing particular amino acids that complex gold. Given the fascination of people for gold it is not surprising that people experimented with gold for medical treatments. In the 8th century alchemists attempted to prepare elixirs from metallic gold. These were supposed to cure all diseases as well as conferring eternal youth.

In the 13th century gold was disolved in aqua regia and the resultant mixture mixed with oil of rosemary or other "essential oils" to form aurum potabile. This was said to cure leprosy. Following this gold treatments were often often used for any number of conditions but with little evidence that they actually worked. Things started to get a little more interesting in the 1890s when it was found that the gold cyanide salt K[Au(CN)2] killed the microorganism responsible for tuberculosis. This was used to treat tuberculosis but, perhaps unsurprisingly, with considerable toxicity problems. After the first world war gold thiol drugs were developed. These are Au(I) complexes such as sodium aurothiosulphate ("Sanocrysin"), sodium aurothiomalate ("Myocrisin"), and aurothioglucose ("Solganal-B-oleosum"). These are less toxic than K[Au(CN)2] but eventually fell out of favour. However sodium aurothiosulphate and aurothioglucose ("Solganal-B-oleosum") are in use today for the treatment of rheumatoid arthritis following successful drug trials.

Some patients do suffer side effects. More recently gold phosphine complexes of the type [AuX(PR3)] (X = halide, R = alkyl) were tested for anti-inflammatory effects. They possess the advantage that they may be taken orally whereas earlier drugs such as sodium aurothiomalate must be injected. The gold phosphine drugs seem less toxic to the kidneys and the best therapeutic effect is observed for [AuCl(PEt3)]. Auranofin (brand name Ridaura) is an organogold compound classified by the World Health Organization as an antirheumatic agent.

IUPAC Name: gold(1+); 3,4,5-triacetyloxy-6-(acetyloxymethyl)oxane-2-thiolate; triethylphosphanium Canonical SMILES: CC[PH+](CC)CC.CC(=O)OCC1C(C(C(C(O1)[S-])OC(=O)C)OC(=O)C)OC(=O)C.[Au+] InChI: InChI=1S/C14H20O9S.C6H15P.Au/c1-6(15)19-5-10-11(20-7(2)16)12(21-8(3)17) 13(14(24)23-10)22-9(4)18;1-4-7(5-2)6-3;/h10-14,24H,5H2,1-4H3;4-6H2, 1-3H3;/q;;+1 Other drugs that perhaps have anti-inflammatory effects include Au{(

SCH(CH2CO2H)(CO2H)}(PR3)] (R = alkyl, alkoxy, phenyl).

The gold isotope 198Au is used for treating cancer and other conditions. Further reading: Peter J. Sadler, "The biological chemistry of gold", Gold Bulletin, 1976, 9, 110-118 . Sabine L Best and Peter J. Sadler, "Gold Drugs: Mechanism of Action and Toxicity", Gold Bulletin, 1996, 29, 87-93 . Gold is found as the free element in nature and associated with quartz, pyrite and other minerals. Two thirds of the world's supply comes from South Africa. Much of the USA production is from the states South Dakota and Nevada. Gold is found in sea water (about 5-6 g in a million tonnes of seawater), but no effective economic process has been designed (yet) to extract it from this source. Abundances for gold in a number of different environments. More abundance data » Location Second ionisation energy : 1980 kJ mol‑1 Isolation Isolation : it would not normally be necessary to make gold in the laboratory as it is readily available commercially.

The most romantic way to extract gold is by panning it out from a stream in some pleasant valley but most such sources are now depleted. Panning relies upon the density of gold (which is very high) being much greater than that of the sand and other particulates. It therefore settles to the bottom of the pan. The amount of gold recoverable in this way is declining. One suggestion regarding the golden fleece in the Jason and the Argonauts story (Greek mythology) is that the golden fleece is a consequence of gold mining. There are suggestions that, perhaps 1500 years ago sheep fleeces were stretched out over wooden frames and be submerged in streams. Gold particles swept down from from upstream deposits would then become embedded in them. The fleeces were then dried in trees before shaking or combing the gold out. Similarly, sheep fleeces may have been used on washing tables at alluvial gold mines with much the same effect. Perhaps such methods predated panning of gold from river sands. Today, more often than not, gold is extracted from ores. These ores often contain relatively little gold. Some of these processes cause environmental concern. Much gold is recovered from ores that are low in gold concentration using a cyanide extraction process.

Cyanide extraction was first used around 1887, when the MacArthur-Forrest Process was developed in Glasgow by John Stewart MacArthur. Many worry about the envoronmental effects of the cyanide extraction process and the risks of using cyanide on a large scale. There are three main steps. The first step is leaching - the ore is crushed to a powder so as to expose the small gold particles. and mixed with water. The resulting mixture of powdered ore and water (the slury) is then reacted with cyanide in the presence of oxygen. 4Au(s) + 8CN-(aq) + 2H2O(l) + O2(g) → 4[Au(CN)2]-(aq) + 4OH-(aq) The result is that electrons from oxygen are used to convert the gold metal into a Au(I) complex, [Au(CN)2]-. The acidity of the process must be slightly alkaline (pH 10.1 for instance) to minimise the release of highly toxic hydrogen cyanide while optimising the leaching rate. The next stage is concentration. Once in solution the gold must be converted back to gold metal.

One way to do this is by adsorption of the gold onto activated carbon. Most of the impurities are left behind in the solution. This would appear to cause some anion exchange of [Au(CN)2]- with anions associated with the carbon, the precipitation of insoluble AuCN, and the formation of some metallic gold within the carbon pore structure. The final step is recovery and refining. Gold is stripped from the carbon by mixing it with NaCN and NaOH at 1108C forming a new solution of [Au(CN)2]-. This solution is now fairly pure as the activated carbon process removes many of the impurities. The gold is then converted back to elemental gold in the following electrolysis reactions known as "electrowinning": At the anode: 4OH- → O2 + 2H2O +4e- At the cathode: e- + [Au(CN)2]- → Au + 2CN- Overall: 4OH- + 4[Au(CN)2]- → 4Au + 8CN- + O2 + 2H2O The gold is "won" onto stainless steel electrodes or precipitated out as a fine black mud.

The mud is then smelted and poured into moulds to make gold ingots. As an laternative to this, zinc powder is added to the solution or reasonably pure of [Au(CN)2]-. This results in a metal displacement reaction: 2[Au(CN)2]-(aq) + Zn(s) -> [Zn(CN)4]2-(aq) + 2Au(s) As before a fine black 'mud' of gold and residual zinc precipitates from the solution, which is then smelted. Extraction of gold from seawater There is some gold in seawater, but the concentration of dissolved gold is very low, perhaps 10 ng l-1. The most determined attempt to recover gold from sea water was undertaken by Fritz Haber, [F. Haber, Z. Angew. Chem. 1927, 40, 303.], who researched the matter extensively after the First World War. He wanted to find a way to pay Germany's war reparation debts. He developed a method involving gold reduction to the metal by sodium polysulfide and removal using sulphur-coated sand filters.

Four expeditions were made on ships equipped with the extraction technology but with disappointing results. Following this Haber estimated the gold concentration in sea water to be 4 ng l-1, just one-thousandth of the amount which he had expected. With the current estimate for the concentration of gold in sea water as 10 ng-1 and the total volume of the oceans at 1.37 x 109 km3, then the total quantity of gold dissolved in sea water is calculated to be 13.7 million tons. A lot of gold, but not extractable on a commercial basis as yet. Gold isotopes Read more » Gold is monoisotopic consisting completely of 197Au. However there are a number of radioisotopes, some of which are listed. The gold isotope 198Au is used for treating cancer and other conditions. In the form of a gold colloid, 198Au has a diagnostic use for liver imaging and a therapeutic use in treatment of widespread abdominal carcinomatosis with ascites; carcinomatosis of pleura with effusion; lymphomas; interstitially in metastatic tumour.

While there is a certain risk from the β-decay of 198Au the calculation is that the benefits outweight the risks. Gold Facts - Periodic Table of the Chemical Elements Gold Facts Chemical & Physical Properties of Gold Nugget of native gold from the Washington mining district, California. Aramgutan, Wikipedia Commons Gold is an element that was known to ancient man and has always been prized for its color. Here is a collection of facts about this important metal: Atomic Number: 79 Electron Configuration : [Xe]6s14f145d10 Word Origin: Sanskrit Jval; Anglo-Saxon gold; meaning gold - also Latin aurum, shining dawn Isotopes: There are 36 known isotopes of gold ranging from Au-170 to Au-205. There is only one stable isotope of gold: Au-197. Gold-198, with a half-life of 2.7 days, has been used to treat cancer and other illnesses.

Density (g/cc): 19.3 Ionic Radius : 85 (+3e) 137 (+1e) Specific Heat (@20°C J/g mol): 0.129 continue reading below our video 4 Tips for Improving Test Performance First Ionizing Energy (kJ/mol): 889.3 Oxidation States: 3, 1. The oxidation states -1, +2 and +5 exist but are rare. CAS Registry Number : 7440-57-5 Properties: In mass, gold is a yellow-colored metal, although it may be black, ruby, or purple when finely divided. Gold is a good conductor of electricity and heat. It is not affected by exposure to air or to most reagents. It is inert and a good reflector of infrared radiation. Gold is usually alloyed to increase its strength. Pure gold is measured in troy weight, but when gold is alloyed with other metals the term karat is used to express the amount of gold present. Uses: Gold is used in coinage and is the standard for many monetary systems. Gold is used for jewelry, dental work, plating, and reflectors.

Chlorauric acid (HAuCl4) is used in photography for toning silver images. Disodium aurothiomalate, administered intramuscularly, is a treatment for arthritis. Sources: Gold is found as the free metal and in tellurides. It is widely distributed and almost always associated with pyrite or quartz. Gold is found in veins and in alluvial deposits. Gold occurs in sea water in the amount of 0.1 to 2 mg/ton, depending on the location of the sample. Gold Trivia: Gold is one of the few elements that can be found in its native state. Gold is the most malleable and ductile metal . One ounce of gold can be beaten out to 300 ft2 or stretched into a wire 2000 kilometers long (1 μm thick). The melting point of gold is an assigned value, which serves as a calibration point for the International Temperature Scale and International Practical Temperature Scale. The gold ion in the +1 oxidation state (Au(I)+) is called the aurous ion. The gold ion in the +3 oxidation state (Au(III)3+) is called the auric ion.

Compounds containing gold in the -1 oxidation state are called aurides. (Cesium and rubidium can form auride compounds) Gold is one of the noble metals . Noble metal is an alchemical term for metals that do not corrode under normal conditions. Gold is the seventh most dense metal. Metallic gold has no odor or taste. Gold has been used as jewelry since prehistoric times. Today, gold in jewelry is not 'pure' gold. Jewelry gold is made of many different gold alloys . Gold is resistant to most acids. The acid aqua regia is used to dissolve gold. Elemental gold metal is considered non-toxic and occasionally used as a food additive. Transmuting lead into gold was one of the major gold of the alchemists. Modern nuclear chemists have found methods to accomplish this historic task . Quiz: Ready to test your gold facts knowledge? Take the Gold Facts Quiz .

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952) International Atomic Energy Agency ENSDF database (Oct 2010) AU - definition of AU by The Free Dictionary AU - definition of AU by The Free Dictionary the internet domain name for (Computer Science) Australia 2. (General Physics) Also: a.u. angstrom unit 3. (Astronomy) Also: a.u. astronomical unit AU Noun 1.

Au - a soft yellow malleable ductile (trivalent and univalent) metallic element; occurs mainly as nuggets in rocks and alluvial deposits; does not react with most chemicals but is attacked by chlorine and aqua regia gold foil - foil made of gold gold leaf - a very thin form of gold foil gold - coins made of gold noble metal - any metal that is resistant to corrosion or oxidation 24-karat gold , pure gold - 100 per cent gold gold dust - the particles and flakes (and sometimes small nuggets) of gold obtained in placer mining dental gold - an alloy of gold used in dentistry green gold - a gold alloy (at least 14 karat gold with silver or silver and cadmium) that has a green appearance guinea gold - 22-karat gold from which guinea coins were made graphic tellurium , sylvanite - a silver-white mineral consisting of silver gold telluride; a source of gold in Australia and America 2.

AU - a unit of length used for distances within the solar system; equal to the mean distance between the Earth and the Sun (approximately 93 million miles or 150 million kilometers) Au | Define Au at Dictionary.com au [oh] /oʊ/ (Show IPA). French. 1. to the; at the; with the. Expand Examples from the Web for au Expand What I Saw in Haiti Buck Close January 14, 2010 Sure, she was more expensive than an au pair, but, we congratulated ourselves, she spoke English and she knew what she was doing. The One Good Thing Michele Bachmann Did: Proudly Blurt Out Her Age Judith Newman January 7, 2012 Historical Examples I knew he had never been to Germany before, and was au courant with the harmless nature of his mission. British Dictionary definitions for au Expand Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd.

1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Word Origin and History for au Expand Au chemical symbol for "gold," from Latin aurum "gold" (see aureate ). French, "at the, to the," from Old French al, contraction of a le, with -l- softened to -u-, as also poudre from pulverem, chaud from calidus, etc. Used in many expressions in cookery, etc., which have crossed the Channel since 18c., e.g. au contraire, literally "on the contrary;" au gratin, literally "with scrapings;" au jus, literally "with the juice." Online Etymology Dictionary, © 2010 Douglas Harper The symbol for the element gold. AU abbr.

Latin auris utraque (each ear) The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company. (gōld) Symbol Au A soft, shiny, yellow element that is the most malleable of all the metals. It occurs in veins and in alluvial deposits. Because it is very durable, resistant to corrosion, and a good conductor of heat and electricity, gold is used as a plated coating on electrical and mechanical components. It is also an international monetary standard and is used in jewelry and for decoration. Atomic number 79; atomic weight 196.967; melting point 1,063.0°C; boiling point 2,966.0°C; specific gravity 19.32; valence 1, 3. See Periodic Table . See Note at element . The American Heritage® Science Dictionary Copyright © 2002. Published by Houghton Mifflin. All rights reserved.

Question: Au is the chemical symbol for what?
Answer: Gold