Am-241 and Am-243 are the isotopes with the longest half-lifes (432.2 years and 7,370 years, respectively), and are alpha-ray and gamma-ray emitters used as radiation sources in research, radiography, and smoke alarms. Atomic number 95; melting point 1176°C; boiling point 2011°C; specific gravity 12; valence 3, 4, 5, 6. Around 3678 BBY, Darth Marr and several other Dark Councilors confronted the Sith Lord Calypho on the world of Korriban, arresting him for heresy just as. Mine isotope-5, a substance capable of twisting gravitational and electromagnetic fields, making it a potent power source, which the Empire desperately needed for.
• • • Gold is a with symbol Au (from: aurum) and 79. In its purest form, it is a bright, slightly reddish yellow, dense, soft,, and.
Chemically, gold is a and a. It is one of the least reactive chemical elements and is solid under. Gold often occurs in free elemental (native) form, as or grains, in, in, and in. It occurs in a series with the native element (as ) and also naturally with and. Less commonly, it occurs in minerals as gold compounds, often with (). Download 2012 Quickbooks.
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Gold is thought to have been produced in, from the of, and to have been present in the from which the formed. Because the Earth was molten, almost all of the gold present in the probably sank into the. Therefore, most of the gold that is in the Earth's and is thought to have been delivered to Earth later, by during the, about 4 billion years ago. Gold is resistant to most, though it does dissolve in, a mixture of and, which forms a soluble. Gold is insoluble in, which dissolves silver and, a property that has long been used to gold and to confirm the presence of gold in metallic objects, giving rise to the term. Gold also dissolves in solutions of, which are used in and. Gold dissolves in, forming alloys, but this is not a.
Historically, the value of gold was rooted in its relative rarity, easy handling and minting, easy smelting and fabrication, resistance to and other () and its distinctive color. As a, gold has been used for,, and other throughout.
In the past, a was often implemented as a, but gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a system after 1976. A total of 186,700 of gold exists above ground, as of 2015. The world consumption of new gold produced is about 50% in jewelry, 40% in, and 10% in. Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity have led to its continued use in corrosion resistant in all types of computerized devices (its chief industrial use).
Gold is also used in shielding, production,, and. Certain are still used as in medicine. As of 2016, the gold producer by far was with 450 tonnes. A gold nugget of 5 millimetres (0.20 in) in diameter (bottom) can be expanded through hammering into a of about 0.5 square metres (5.4 sq ft).,.
Gold is the most of all metals; a single gram can be beaten into a sheet of 1 square meter, and an 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, making them useful as infrared (radiant heat) shields in visors of heat-resistant suits, and in sun-visors for. Gold is a good and.
Gold has a density of 19.3 g/cm 3, almost identical to that of at 19.25 g/cm 3; as such, tungsten has been used in of, 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 is 11.34 g/cm 3, and that of the densest element,, is 22.588 ± 0.015 g/cm 3.
Different colors of –Au– alloys Whereas most metals are gray or silvery white, gold is slightly reddish-yellow. This color is determined by the frequency of among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to affecting the around gold atoms.
Similar effects impart a golden hue to metallic. Common colored gold alloys include the distinctive eighteen-karat 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 alloys, and both may be used to produce police and other. White gold alloys can be made with. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as. Blue gold can be made by alloying with, and purple gold can be made by alloying with.