Gold - Wikipedia, the free encyclopedia. Gold, 7. 9Au. General properties. Name, symbolgold, Au. Pronunciation. GOHLDAppearancemetallic yellow. Gold in the periodic table. Atomic number(Z)7. Group, blockgroup 1. Introducing the new Microsoft Band. Live healthier and achieve more. Zac Brown Band Zamily Fan Club, website and official merchandise. February 16, 2016 –The Church will be returning to North America for a limited 16-date tour beginning on April 8th in Dallas, TX and wrapping with a two-night stand in Evanston, IL on April 25th & 26th. Relax and enjoy a range of coffees, hot and cold drinks and light refreshments in our conservatory-style seating area. Apple Watch Series 2 has built-in GPS and water resistance to 50 meters. Choose from aluminum, stainless steel, Nike+, Herm. Buy now with fast, free shipping. Lyrics and chord changes to popular country songs, arranged alphabetically by artist and album or CD. Gold, 79 Au; General properties; Name, symbol: gold, Au: Pronunciation / Time Doctor will show you exactly how time is spent in your company and boost productivity. Periodperiod 6. Element category transition metal. Standard atomic weight (. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable and ductilemetal. Chemically, gold is a transition metal and a group 1. It is one of the least reactive chemical elements, and is solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as nuggets or grains, in rocks, in veins and in alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold's atomic number of 7. It is thought to have been produced in supernova nucleosynthesis and from the collision of neutron stars. Because the Earth was molten when it was just formed, almost all of the gold present in the early Earth probably sank into the planetary core. Therefore, most of the gold that is present today in the Earth's crust and mantle is thought to have been delivered to Earth later, by asteroid impacts during the Late Heavy Bombardment, about 4 billion years ago. The acid mixture causes the formation of a soluble tetrachloroaurateanion. It is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold also dissolves in alkaline solutions of cyanide, which are used in mining and electroplating. Gold dissolves in mercury, forming amalgam alloys, but this is not a chemical reaction. Gold is a precious metal used for coinage, jewelry, and other arts throughout recorded history. In the past, a gold standard was often implemented as a monetary policy within and between nations, but gold coins ceased to be minted as a circulating currency in the 1. The historical value of gold was rooted in its relative rarity, easy handling and minting, easy smelting and fabrication, resistance to corrosion and other chemical reactions (nobility), and distinctive color. The world consumption of new gold produced is about 5. Gold is also used in infrared shielding, colored- glass production, gold leafing, and tooth restoration. Certain gold salts are still used as anti- inflammatories in medicine. Etymology. This word is derived from the same root (Proto- Indo- European *h. Gold leaf can be beaten thin enough to become transparent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red. By comparison, the density of lead is 1. The oxidation state of gold in its compounds ranges from . Au(I), referred to as the aurous ion, is the most common oxidation state with soft ligands such as thioethers, thiolates, and tertiary phosphines. Au(I) compounds are typically linear. A good example is Au(CN)2. The binary gold halides, such as Au. Cl, form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives. The gold atom centers in Au(III) complexes, like other d. Gold does not react with oxygen at any temperature. Powdered gold reacts with chlorine at 1. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors. Caesium auride is perhaps the most famous. Gold is unaffected by most acids. It does not react with hydrofluoric, hydrochloric, hydrobromic, hydriodic, sulfuric, or nitric acid. It does react with aqua regia, a mixture of nitric and hydrochloric acids, and with selenic acid. Aqua regia, a 1: 3 mixture of nitric acid and hydrochloric acid, dissolves gold. Nitric acid oxidizes the metal to +3 ions, but only in minute amounts, typically undetectable in the pure acid because of the chemical equilibrium of the reaction. However, the ions are removed from the equilibrium by hydrochloric acid, forming Au. Cl. 4. It does not react with aqueous, solid, or moltensodium or potassium hydroxide. It does however, react with sodium or potassium cyanide under alkaline conditions when oxygen is present to form soluble complexes. Gold ions in solution are readily reduced and precipitated as metal by adding any other metal as the reducing agent. The added metal is oxidized and dissolves, allowing the gold to be displaced from solution and be recovered as a solid precipitate. Less common oxidation states. Less common oxidation states of gold include . Caesium auride (Cs. Au), for example, crystallizes in the caesium chloride motif. The evaporation of a solution of Au(OH)3 in concentrated H2. SO4 produces red crystals of gold(II) sulfate, Au. SO4)2. Originally thought to be a mixed- valence compound, it has been shown to contain Au. I) ion, Hg. 2+2 . The interaction is estimated to be comparable in strength to that of a hydrogen bond. Mixed valence compounds. Well- defined cluster compounds are numerous. A representative example is the octahedral species . Gold chalcogenides, such as gold sulfide, feature equal amounts of Au(I) and Au(III). Color. Different colors of Ag- Au- Cu alloys. Whereas most other pure metals are gray or silvery white, gold is slightly reddish yellow. The frequency of these oscillations lies in the ultraviolet range for most metals, but it falls into the visible range for gold due to subtle relativistic effects that affect the orbitals around gold atoms. Alloys containing palladium or nickel are also important in commercial jewelry as these produce white gold alloys. Less commonly, addition of manganese, aluminium, iron, indium and other elements can produce more unusual colors of gold for various applications. Thirty- six radioisotopes have been synthesized ranging in atomic mass from 1. The most stable of these is 1. Au with a half- life of 1. The least stable is 1. Au, which decays by proton emission with a half- life of 3. Most of gold's radioisotopes with atomic masses below 1. The exceptions are 1. Au, which decays by electron capture, and 1. Au, which decays most often by electron capture (9. Within that range, only 1. Au, 1. 80. Au, 1. Au, 1. 82. Au, and 1. Au do not have isomers. Gold's most stable isomer is 1. Au with a half- life of 2. Gold's least stable isomer is 1. Au with a half- life of only 7 ns. Au has three decay paths: . No other isomer or isotope of gold has three decay paths. Alloys with lower karat rating, typically 2. Copper is the most commonly used base metal, yielding a redder color. Fourteen- karat gold- copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges. Blue gold can be made by alloying with iron and purple gold can be made by alloying with aluminium, although rarely done except in specialized jewelry. Blue gold is more brittle and therefore more difficult to work with when making jewelry. White gold alloys can be made with palladium or nickel. White 1. 8- karat gold containing 1. Nickel is toxic, however, and its release from nickel white gold is controlled by legislation in Europe. High- karat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. The Japanese craft of Mokume- gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood- grain effects. By 2. 01. 4 the gold jewelry industry was escalating despite a dip in gold prices. Demand in the first quarter of 2. World Gold Council report. Investment. Gold prices (US$ per troy ounce), in nominal US$ and inflation adjusted US$. Many holders of gold store it in form of bullion coins or bars as a hedge against inflation or other economic disruptions. However, economist Martin Feldstein does not believe gold serves as a hedge against inflation or currency depreciation. In 2. 00. 6, the United States Mint began producing the American Buffalo gold bullion coin with a purity of 9. The Australian Gold Kangaroos were first coined in 1. Australian Gold Nugget but changed the reverse design in 1. Other modern coins include the Austrian. Vienna Philharmonic bullion coin and the Chinese Gold Panda. Electronics connectors. Only 1. 0% of the world consumption of new gold produced goes to industry. For example, according to the World Gold council, a typical cell phone may contain 5. But since nearly one billion cell phones are produced each year, a gold value of 5. For example, gold is used in the connectors of the more expensive electronics cables, such as audio, video and USB cables. The benefit of using gold over other connector metals such as tin in these applications has been debated; gold connectors are often criticized by audio- visual experts as unnecessary for most consumers and seen as simply a marketing ploy. However, the use of gold in other applications in electronic sliding contacts in highly humid or corrosive atmospheres, and in use for contacts with a very high failure cost (certain computers, communications equipment, spacecraft, jet aircraft engines) remains very common. Fine gold wires are used to connect semiconductor devices to their packages through a process known as wire bonding. The concentration of free electrons in gold metal is 5. Gold is highly conductive to electricity, and has been used for electrical wiring in some high- energy applications (only silver and copper are more conductive per volume, but gold has the advantage of corrosion resistance). For example, gold electrical wires were used during some of the Manhattan Project's atomic experiments, but large high- current silver wires were used in the calutron isotope separator magnets in the project. It's estimated that 1. Japan. Toi museum, Japan. Gold solder is used for joining the components of gold jewelry by high- temperature hard soldering or brazing.
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