Reed Relays and
Electronics India Limited
Manufacturer of Reed Switches, Reed Sensors and Reed-based products
Reed Relays and Electronics India Limited Incorporated in 1971
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Gold

Gold is a chemical element with the symbol Au (Aurum in Latin) and atomic number 79. It is a dense, soft, malleable and ductile metal with a bright yellow color and luster. Gold is sometimes used as an under-layer in reed switch contacts, but can cause some sticking. Reed Switch leads are plated with Gold to increase the shelf life.

Gold (Wikipedia)

Gold,  79Au
Gold-crystals.jpg
General properties
Appearancemetallic yellow
Standard atomic weight (Ar, standard)196.966570(4)
Gold in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ag

Au

Rg
platinumgoldmercury
Atomic number (Z)79
Groupgroup 11
Periodperiod 6
Blockd-block
Element category  transition metal
Electron configuration[Xe] 4f14 5d10 6s1
Electrons per shell
2, 8, 18, 32, 18, 1
Physical properties
Phase at STPsolid
Melting point1337.33 K ​(1064.18 °C, ​1947.52 °F)
Boiling point3243 K ​(2970 °C, ​5378 °F)
Density (near r.t.)19.30 g/cm3
when liquid (at m.p.)17.31 g/cm3
Heat of fusion12.55 kJ/mol
Heat of vaporization342 kJ/mol
Molar heat capacity25.418 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1646 1814 2021 2281 2620 3078
Atomic properties
Oxidation states−3, −2, −1, +1, +2, +3 +5 (an amphoteric oxide)
ElectronegativityPauling scale: 2.54
Ionization energies
  • 1st: 890.1 kJ/mol
  • 2nd: 1980 kJ/mol
Atomic radiusempirical: 144 pm
Covalent radius136±6 pm
Van der Waals radius166 pm
Color lines in a spectral range
Spectral lines of gold
Other properties
Crystal structureface-centered cubic (fcc)
Face centered cubic crystal structure for gold
Speed of sound thin rod2030 m/s (at r.t.)
Thermal expansion14.2 µm/(m·K) (at 25 °C)
Thermal conductivity318 W/(m·K)
Electrical resistivity22.14 nΩ·m (at 20 °C)
Magnetic orderingdiamagnetic
Magnetic susceptibility−28.0·10−6 cm3/mol (at 296 K)
Tensile strength120 MPa
Young's modulus79 GPa
Shear modulus27 GPa
Bulk modulus180 GPa
Poisson ratio0.4
Mohs hardness2.5
Vickers hardness188–216 MPa
Brinell hardness188–245 MPa
CAS Number7440-57-5
History
Namingfrom Latin aurum, meaning gold
DiscoveryIn the Middle East (before 6000 BCE)
Main isotopes of gold
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
195Au syn 186.10 d ε 195Pt
196Au syn 6.183 d ε 196Pt
β 196Hg
197Au 100% stable
198Au syn 2.69517 d β 198Hg
199Au syn 3.169 d β 199Hg
| references

Gold is a chemical element with symbol Au (from Latin: aurum) and atomic number 79, making it one of the higher atomic number elements that occur naturally. 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. Gold often occurs 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 is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold 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.

A relatively rare element, gold is a precious metal that has been used for coinage, jewelry, and other arts throughout recorded history. In the past, a gold standard was often implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a fiat currency system after 1971.

A total of 186,700 tonnes of gold exists above ground, as of 2015. The world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry. 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 electrical connectors in all types of computerized devices (its chief industrial use). 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. As of 2016, the world's largest gold producer by far was China with 450 tonnes per year.

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