You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Errorf "Password can't be a commonly used password". It can be drawn into a wire of single-atom width, and then stretched considerably before it breaks. Gold leaf can be beaten thin enough to become semi-transparent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red.

Gold has a density of Whereas most metals are gray or silvery white, gold is slightly reddish-yellow. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are also important in commercial jewelry as these produce white gold alloys.

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. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron , and purple gold can be made by alloying with aluminium. Less commonly, addition of manganese , indium , and other elements can produce more unusual colors of gold for various applications.

Colloidal gold , used by electron-microscopists, is red if the particles are small; larger particles of colloidal gold are blue. Gold has only one stable isotope , Au , which is also its only naturally occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from to The most stable of these is Au with a half-life of At least 32 nuclear isomers have also been characterized, ranging in atomic mass from to Gold's most stable isomer is m2 Au with a half-life of 2.

US Consumer Spending Rose More than Expected

Gold's least stable isomer is m2 Au with a half-life of only 7 ns. No other isomer or isotope of gold has three decay paths. The production of gold from a more common element, such as lead , has long been a subject of human inquiry, and the ancient and medieval discipline of alchemy often focused on it; however, the transmutation of the chemical elements did not become possible until the understanding of nuclear physics in the 20th century. The first synthesis of gold was conducted by Japanese physicist Hantaro Nagaoka , who synthesized gold from mercury in by neutron bombardment.

Gold can currently be manufactured in a nuclear reactor by irradiation either of platinum or mercury. Only the mercury isotope Hg, which occurs with a frequency of 0. Other isotopes of mercury can only be converted into other mercury isotopes when irradiated with slow neutrons, some of which beta decay into thallium.

Using fast neutrons , the mercury isotope Hg, which composes 9. This reaction, however, possesses a smaller activation cross-section and is feasible only with un-moderated reactors. It is also possible to eject several neutrons with very high energy into the other mercury isotopes in order to form Hg.

However, such high-energy neutrons can be produced only by particle accelerators. Although gold is the most noble of the noble metals , [30] [31] it still forms many diverse compounds. 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. The binary gold halides , such as AuCl , 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 8 compounds, are typically square planar , with chemical bonds that have both covalent and ionic character. Some free halogens react with gold. Gold does not react with sulfur directly, [38] but gold III sulfide can be made by passing hydrogen sulfide through a dilute solution of gold III chloride or chlorauric acid.

Gold readily dissolves in mercury at room temperature to form an amalgam , and forms alloys with many other metals at higher temperatures. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors. Gold is unaffected by most acids.

It does not react with hydrofluoric , hydrochloric , hydrobromic , hydriodic , sulfuric , or nitric acid. It does react with selenic acid , and is dissolved by aqua regia , a mixture of nitric acid and hydrochloric acid. Gold is similarly unaffected by most bases. It does not react with aqueous , solid , or molten sodium or potassium hydroxide. It does however, react with sodium or potassium cyanide under alkaline conditions when oxygen is present to form soluble complexes.

skolko na gm zoloto v singapure

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. Caesium auride CsAu , for example, crystallizes in the caesium chloride motif; [39] rubidium, potassium, and tetramethylammonium aurides are also known.

Some gold compounds exhibit aurophilic bonding , which describes the tendency of gold ions to interact at distances that are too long to be a conventional Au—Au bond but shorter than van der Waals bonding.

• Why are some of my events grayed out? | Help Center;
• Forexpf Ru Chart Copper;
• what is ibr rate in forex;

The interaction is estimated to be comparable in strength to that of a hydrogen bond. Well-defined cluster compounds are numerous. Medicinal applications of gold and its complexes have a long history dating back thousands of years.

Accessibility links

Both gold I and gold III compounds have been investigated as possible anti-cancer drugs. Stable complexes can be generated using different types of bi-, tri-, and tetradentate ligand systems, and their efficacy has been demonstrated in vitro and in vivo.

• SilverPrice;
• Gold Jun 21 (GC=F) Stock Price, News, Quote & History - Yahoo Finance.
• Metals, Gold & Silver Prices - Commodities | ?

Gold is thought to have been produced in supernova nucleosynthesis , and from the collision of neutron stars , [48] and to have been present in the dust from which the Solar System formed. Traditionally, gold in the universe is thought to have formed by the r-process rapid neutron capture in supernova nucleosynthesis , [50] but more recently it has been suggested that gold and other elements heavier than iron may also be produced in quantity by the r-process in the collision of neutron stars.

This amount, along with estimations of the rate of occurrence of these neutron star merger events, suggests that such mergers may produce enough gold to account for most of the abundance of this element in the universe. Because the Earth was molten when it was formed , almost all of the gold present in the early Earth probably sank into the planetary core.

Therefore, most of the gold that is in the Earth's crust and mantle has in one model thought to have been delivered to Earth later, by asteroid impacts during the Late Heavy Bombardment , about 4 billion years ago. Gold which is reachable by humans has, in one case, been associated with a particular asteroid impact. The asteroid that formed Vredefort crater 2. The gold-bearing Witwatersrand rocks were laid down between and million years before the Vredefort impact.

What the Vredefort impact achieved, however, was to distort the Witwatersrand basin in such a way that the gold-bearing rocks were brought to the present erosion surface in Johannesburg , on the Witwatersrand , just inside the rim of the original km mi diameter crater caused by the meteor strike. The discovery of the deposit in launched the Witwatersrand Gold Rush. Notwithstanding the impact above, much of the rest of the gold on Earth is thought to have been incorporated into the planet since its very beginning, as planetesimals formed the planet's mantle, early in Earth's creation.

In , an international group of scientists, established that gold "came to the Earth's surface from the deepest regions of our planet", [63] the mantle , evidenced by their findings at Deseado Massif in the Argentinian Patagonia. On Earth, gold is found in ores in rock formed from the Precambrian time onward.

Electrum's color runs from golden-silvery to silvery, dependent upon the silver content. The more silver, the lower the specific gravity. Native gold occurs as very small to microscopic particles embedded in rock, often together with quartz or sulfide minerals such as "fool's gold", which is a pyrite.

The metal in a native state is also found in the form of free flakes, grains or larger nuggets [65] that have been eroded from rocks and end up in alluvial deposits called placer deposits. Such free gold is always richer at the surface of gold-bearing veins [ clarification needed ] owing to the oxidation of accompanying minerals followed by weathering, and washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets. Gold sometimes occurs combined with tellurium as the minerals calaverite , krennerite , nagyagite , petzite and sylvanite see telluride minerals , and as the rare bismuthide maldonite Au 2 Bi and antimonide aurostibite AuSb 2.

Gold also occurs in rare alloys with copper , lead , and mercury : the minerals auricupride Cu 3 Au , novodneprite AuPb 3 and weishanite Au, Ag 3 Hg 2. Recent research suggests that microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits.

Another recent study has claimed water in faults vaporizes during an earthquake, depositing gold. When an earthquake strikes, it moves along a fault. Water often lubricates faults, filling in fractures and jogs. About 10 kilometres 6. During an earthquake, the fault jog suddenly opens wider. The water inside the void instantly vaporizes, flashing to steam and forcing silica, which forms the mineral quartz, and gold out of the fluids and onto nearby surfaces. The world's oceans contain gold.

At 10 parts per quadrillion the Earth's oceans would hold 15, tonnes of gold. A number of people have claimed to be able to economically recover gold from sea water , but they were either mistaken or acted in an intentional deception. Prescott Jernegan ran a gold-from-seawater swindle in the United States in the s, as did an English fraudster in the early s. After analysis of 4, water samples yielding an average of 0. The earliest recorded metal employed by humans appears to be gold, which can be found free or " native ". Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, c.

The oldest known map of a gold mine was drawn in the 19th Dynasty of Ancient Egypt — BC , whereas the first written reference to gold was recorded in the 12th Dynasty around BC. One of the earliest known maps, known as the Turin Papyrus Map , shows the plan of a gold mine in Nubia together with indications of the local geology.

Contact | A Critical Engagement

The primitive working methods are described by both Strabo and Diodorus Siculus , and included fire-setting. Large mines were also present across the Red Sea in what is now Saudi Arabia. Gold is mentioned in the Amarna letters numbered 19 [79] and 26 [80] from around the 14th century BC. Gold is mentioned frequently in the Old Testament , starting with Genesis at Havilah , the story of the golden calf , and many parts of the temple including the Menorah and the golden altar.

In the New Testament , it is included with the gifts of the magi in the first chapters of Matthew. The Book of Revelation describes the city of New Jerusalem as having streets "made of pure gold, clear as crystal". Exploitation of gold in the south-east corner of the Black Sea 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 around BC.

From the 6th or 5th century BC, the Chu state circulated the Ying Yuan , one kind of square gold coin.