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Gold is a chemical element with the symbol Au (from Latin: aurum) and the atomic number 79. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable and ductile metal. Chemically, gold is a transition metal and a group 11 element. 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).

No precious metallic is as mythical and delightful as Gold. Its rarity, splendor, and enigma have supplied it with status as a treasured commodity at some point of the records of humanity. Gold has always been used as a monetary trendy, and historical gold jewellery and ornaments courting returned centuries have been determined at some stage in the world. Gold has continually been and stays the most important jewelry factor, with most valuable jewelry pieces constructed from Gold or inlaid with a Gold putting.

Gold resists attack by using man or woman acids, however aqua regia (literally "royal water", a aggregate of nitric acid and hydrochloric acid) can dissolve it. The acid combination causes the formation of a soluble tetrachloroaurate anion. It is insoluble in nitric acid, which dissolves silver and base metals, a assets that has lengthy been used to refine gold and to verify the presence of gold in metal objects, giving rise to the term acid check. Gold also dissolves in alkaline answers of cyanide, that are utilized in mining and electroplating. Gold dissolves in mercury, forming amalgam alloys, but this isn't a chemical reaction.

Gold is a precious metal used for coinage, jewelry, and different arts all through recorded history. In the past, a gold general was regularly applied as a monetary policy inside and among countries, however gold coins ceased to be minted as a circulating currency inside the 1930s, and the sector gold standard became abandoned for a fiat foreign money system after 1976. The historic cost of gold was rooted in its relative rarity, easy dealing with and minting, smooth smelting and fabrication, resistance to corrosion and other chemical reactions (the Aristocracy), and specific color.

Gold is the most malleable of all metals; a single gram can be beaten into a sheet of 1 square meter, and an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red. Such semi-transparent sheets also strongly reflect infrared light, making them useful as infrared (radiant heat) shields in visors of heat-resistant suits, and in sun-visors for spacesuits. Gold is a good conductor of heat and electricity and reflects infrared radiation strongly.

Gold has a density of 19.3 g/cm3, almost identical to that of tungsten at 19.25 g/cm3; as such, tungsten has been used in counterfeiting of gold bars, such as by plating a tungsten bar with gold, or taking an existing gold bar, drilling holes, and replacing the removed gold with tungsten rods. By comparison, the density of lead is 11.34 g/cm3, and that of the densest element, osmium, is 22.588 ± 0.015 g/cm3.

Chemical FormulaAu
ColourMetallic, Yellow
Hardness2.5 - 3
Crystal SystemIsometric
SG15 - 19
Double RefractionNone
Mineral ClassGold

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